Fuel Pressure reg

[Russ]

Tested my pres reg today,not sure if it duff. I thought when the pump primes the pressure reg should be closed? When I primed mine fuel came out of the spill port pipe,not a huge amount but im concerned its not seating correctly. Also when I removed the fuel rail I put a vac pump on it but it did not release a huge amount of fuel.

I have a brand new montego one the one from the later cars which sits on the end of the round cast bus rail located by two bolts.
Has anyone got one that is known to work from a car with the square section bus rail where the reg is a push fit on the rail and a screw union to the spill pipe.

Cheers

A very hopeful Russ!
07798 576081

[E_T_V]

Fuel pressure reg is designed to keep a certain pressure in the fuel rail (above the pressure of the inlet manifold). Its normal for some fuel to come out when you prime the pump. The pump pressurises the rail and then the excess pressure is returned back to the pump. If you turned the pump on continuously then you've get a continuous stream out of the spill port (which would return to the tank). I'm not saying that it isn't faulty but the behavious observed is normal so far. Is the air pipe connecting it to the manifold intact and not leaking? If it leaks then it'll produce the wrong fuel pressure even if the reg itself is perfectly ok.

[Russ]

The vac pipe is fine, as you may have realised the flat spot is back:banghead: Ive set the pot,had my injectors cleaned the onlt thing i havnt changed is the pres reg. I have a felling it sticking as when I had the rail off I held it over a container and operated the vac pump a bit of fuel came out but not a lot ,when I took the injectors out there was alot still in. Also if you crack the inlet union open there is not a lot of pressure. The pump is the second brand new one ,new filter ,fuel sprays out if you operate the pump with the pipe off. So other than the ecu the pres reg is all thats left.

Cheers

Russ

[G Force]

Hi Russ if you just rely on the priming period 2-3 seconds to bring the rail up to full pressure then you will not get a large amount of fuel from the return because the regulator is there to allow pressure to build up in the rail to 2.5bar.

If you run the pump constantly by turning the ignition on and earth the pink brown wire on the fuel pump relay you will find that the fuel pressure regulatator behaves more like you expect. But the trouble is in just seeing how much fuel is returned to the tank it does not tell you anything useful about fuel pressure, to test the fuel pressure regulator and pump is working correctly you need a suitable pressure gauge.


With the gauge installed you can easily see what the pressure is at idle (2.0bar later model) (2.5 bar early) and with the vac pipe removed(2.5bar later models) (3 bar early). If you briefly clamp the return hose the pressure should rise to approx 5 bar and no more than 6.5bar.

You can also check that the pressure is holding in the rail when the engine is turned off. If it is not holding then clamp the return hose, if the pressure then holds then the regulator is faulty.

If the pressure still does not hold with engine off, then clamp the fuel feed pipe before the gauge, if it then holds the fuel pump non return valve is faulty. If the pressure still drops with both feed & return pipes clamped off, you must have an injector leak.


Gary:)

[G Force]

On the subject of the flat spot I would still be suspicious of water in the tank as it did improve for a while when you fit a new filter.

You could pump out a few litres and let the fuel stand overnight in a glass vase to see if anything seperates.

You could also check the throttle pot multiplug connections are clean and tight, sometimes just pulling the plug apart and reconnecting it can effect a cure.

Gary:)

[Russ]

Blanked off the the fuel pres reg today as it was stuck open, took it out for a quick test run. What a difference,no flat spot at all. Ive ordered a new reg and should pick it up tomorrow,£84 + vat so not to cheap and no joy with a secondhand one ,but if it sorts the car out its worth it. I'll now have to reset the CO and base idle. At least the pot is ok they are £115+vat:eek: Thanks again for your suggestions chaps.

Russ

PS Still got the dash to sort....

[G Force]

Hopefully Russ you have found the culprit and a regulator will sort out your flat spot.:D

It might be me just looking on the black side but blanking the fuel return puts the fuel pressure up to above 60psi, and in doing so can mask a whole lot of other problems. But with any luck I will be wrong and you can then concentrate on converting your dash.:)

[Russ]

Its virtually sorted 99% better but not perfect still slight flat spot when driven hard ,I have another idea. When the pump was fitted the union to the pump (its a volvo bosch pump with a different fitting but same spec) it had a pipe that was slightly smaller than the hose. So im going to get a hose with the right fitting on it as it may be restricting pressure.
Found a very helpful rover parts man this morn. The speed sensor i need for dash is either ybe10037 or drc8154 both of which look like the 820 one i have but without the earth, so if i cant get one of those i may try the 820 one.

Cheers
Russ

[Russ]

Changed the pipe on the pump today,no difference at all :banghead:
Im really fed up with this now,ive got my ZR booked in at a rover specialist tomorrow, so im going to see if he can sort it as he has some fastcheck gear but hes not sure what.
Could the fuel ecu be at fault? The only time in the past ive experienced knackered fuel ecu was one that running far too rich cos someone had sparked the batt pos on the airflow meter.
Ive set the throttle pot up perfect but can these fail and give flat spots?

Russ

[G Force]

Could the fuel ecu be at fault?

Ive set the throttle pot up perfect but can these fail and give flat spots?



Hi the ECU could be faulty but on the whole they are reasonably reliable, I have never changed an ECU for your type of fault, but you can't rule it out totally.

The throttle pot can cause flat spots if faulty but again they are pretty reliable. If the throttle pot is faulty it will show up with your multi meter. Once you have set the initial output setting to 325mv as you slowly open the throttle the voltage output should rise smoothly and steadily to around 5v at full throttle. Bad connections from the throttle pot to the ECU are far more common than actual throttle pot failures.

[Russ]

I got a pot off a V8 rangerover,looked the same except for colour coding but the bloody thing is the opposite hand! Ive just spent the last 2 hours removing another one from a mates scrap XJ40 that fits and works but needs the slots filing out to get the right setting but cant be far out, flat spot is still there:mad:
on the plus side i got a full set of fast check gear for the efi today so setting the pot is now very easy,im not sure how the ignition one works and I think there is some adaptors missing from the injection one but the pot set up one is there.
The only thing I havnt changed on this car is fuel ecu which fast check cant test,im wondering if its worth buying one anyway to keep in the boot as a spare,does anyone know if the one from the early digi dash one is the same as later ones as it may be worth getting one of those. incidently one of the fast check modules i got today is for digi dashes.

Cheers

Russ

[G Force]

on the plus side i got a full set of fast check gear for the efi today so setting the pot is now very easy,im not sure how the ignition one works and I think there is some adaptors missing from the injection one but the pot set up one is there.

It is more accurate and gives better results if you use the multimeter to set the throttle pot setting.

There should be a lead for the EFI fast check that connects to the ECU harness. Note it has to be the Electronic Fuel injection Fast Check and Not the Fuel Injection fast check.

The programmed ignition fast check is simple to use, Plug the fast check lead into the Programmed ignition ECU harness and turn the switch on the fast check to static. With the ignition on the correct response is ign & coil LED's illuminated and all 3 left hand LED'S extinguished, ignore the 3 right hand LED'S at this point. Any different response indicates a fault on that particular circuit.

Next turn the switch to dynamic and crank the engine. The correct response is ign & coil and all 3 right hand LED'S illuminated, ignore the 3 left hand LED'S at this point. Any different response indicates a fault on that particular circuit.


The only thing I havnt changed on this car is fuel ecu which fast check cant test,im wondering if its worth buying one anyway to keep in the boot as a spare,does anyone know if the one from the early digi dash one is the same as later ones as it may be worth getting one of those.


The early EFI ECU is different to the later ecu and won't run your car properly because the injection duration is different, but the later ECU is OK to use with the Digi dash.

Gary:)

[Russ]

Im now 99% certain its electrical, disconected the pot and ran it exactly the same as with it connected. Ive tested the wires from the multiplug upto the main engine multiplug and are all ok, the pot is getting the correct voltage but the ecu is doing nothing with the return information.
So ive taken the plunge and ordered another ecu,if its not this at least ill have a spare in the boot.

Cheers

Russ

[G Force]

. Ive tested the wires from the multiplug upto the main engine multiplug and are all ok, the pot is getting the correct voltage but the ecu is doing nothing with the return information.


Have you checked the wires to the ECU plug or just the engine bay multi plug?

[Russ]

Checked both,there seems to be something rattling in the ecu which is not a good sign:eek:
New one should be here in morning

Russ

[G Force]

Checked both,there seems to be something rattling in the ecu which is not a good sign:eek:
Russ

Agreed! should not rattle:eek:

[Russ]

This is really doing my head in now!! Changed ecu ,just the same. Ive now ordered a fuel pres guage to do some more tests. Ive had the fuel line disconnected both ends today and blew it through with an air line still no change.
Whats on the end of the pick up pipe in the tank? I blew a bit of air down that and the fuel bubbled. Im wondering if the new pres reg is no good but it sealed with no vac where the old one didnt.
Thus far ive done
Change air flow meter 5times
Changed map sensor
Changed ecu
Changed pot
Changed fuel pres reg
Dizzy cap
Rotor arm
King lead.
Fuel pump twice
Fuel filter
I recon its fuel side as when I blocked off the return it ran ok

[G Force]

Whats on the end of the pick up pipe in the tank?

On the end of the pick up pipe is a plastic gauze filter. The pipe is sat in a swirl pot, the return pipe also terminates in the swirl pot. The swirling effect of the warm return fuel draws cold fuel from the tank to where the pick up pipe is sat. This ensures cold & denser fuel is always available at the pick up pipe & also help stop fuel surging away from the pick up pipe on accelartion & cornering.

Im wondering if the new pres reg is no good but it sealed with no vac where the old one didnt.


The fuel pressure regulator must be wrong type as the regulator has always been duel pressure on Maestro Montego. If the fuel pressure regulator has an adjusting screw like a FSE or Jaguar type then you can use it if you adjust the fuel pressure to 2.5 bar. Make sure you get the right combination of ECU part no. and fuel pressure regulator. I think I'm right saying your particular car should have an AUU1051 OR AUU1313 with the 2.5bar regulator.

Don't rule out glazed or faulty injectors or contaminated fuel.

Gary:)

[Russ]

Im wondering if i can get that gauze filter off, the pres reg is the right one for the car as I saw the part no.s on the screen your right about the ecu its auu1313 . The injectors have just been reconditioned and its had about 3 tanks of fuel since i got it,and contaminated fuel would cause other running problems.
Im thinking that the original pump was noisey (still had the flat spot) so was changed by the garage,the second was one of those cheap non genuine ones off ebay ,that seized. Now it has a new bosch one which is also a bit noisey.So im thinking are these struggling to suck the fuel from the tank?
Theres no way to remove the pick up pipe from the tank is there? I wonder if i can use a flexible drain unblocker to poke the filter off the end of the pickup pipe? As that would prove my problem without costing anymore money,and it would float and not block the pipe.Are new tanks easy to come by?

Cheers

Russ (on suiside watch!!)

[G Force]

Im wondering if i can get that gauze filter off, the pres reg is the right one for the car as I saw the part no.s on the screen
Russ (on suiside watch!!)

Hi Russ don't let it beat you, you can't fix it hanging from the ceiling :laugh: & it would not be fair on whoever inherited the car:D

Joking aside, I would not try remove the gauze as that will certainly lead to more pump failures (I have had this problem first hand with a fairly new car). It would be worth looking into the tank as ETV has mentioned the possibility of the pickup pipe drawing air somewhere due to corrosion.

The FPR has always had a vac connection, so if yours does not then it is wrong and could have been boxed wrong.

It could be worth you describing the flat spot as it accurs now, as when reading through your other postings it sounds like you have made improvements to the drivabillity along the way.

Try describe flat spot in terms of Engine hot/cold, what revs, what load, full throttle / light throttle, duration of flat spot. You never know it might just make someone think.

I think you will find the fuel pressure gauge a useful diagnostic tool once it arrives.

Stick at it

Gary:)

[Russ]

Right

The flat spot happens whether the engine is hot or cold.
Set off apply full power,1st gear no problems ,up to the red line if you want. Into 2nd pulls ok ,then about 3500rpm power dies then picks up again but the engine does not seem to be making full power,ease the throttle and reapply slowly and all is ok. This also happens when dropping a gear for overtaking. Ive had this before on another car and that was an airflow meter which is why I tried 5 on this!
Im pretty sure ive got low fuel pres as when I removed the pump to bus rail hose today there was hardly any presure and the engine had just been shut down.
There is a vac hose on the pres reg.
My theory of what is happening is
Car sets off from idle slight vac to regulator,pump has had time to get bus rail up to a reasonable pres- engine powers ok. Gear change, throttle shuts,lots of vac ,regulator dumps fuel ,throttle wide open ,regulator shut ,pump cant supply enough fuel ,engine dies.
I cant remember what access you have to tank,they dont seem to be available .Are montego saloon or estate ones the same?

Cheers

Russ

[G Force]

Im pretty sure ive got low fuel pres?


The symptoms you describe do seem to point towards a fuelling problem, & could very easily be fuel pressure.

The fuel pressure gauge should be able to prove this definitively.

It sounds to me as if the engine is probably leaning out when demand for fuel is high i.e. max torque & power. This could be fuel pressure / delivery rate or low delivery due to an injection problem or fuel quality.

The Max fuel pressure test I described should prove any fault with the pick up as the fuel pressure should rise up to 60psi imediately once you clamp the return hose, any slight delay would suggest that the pick up is either restricted or drawing air or a pump problem. You will also be able to rig the gauge up so you can see what is happening to fuel pressure when your driving.

If the gauge is going to be a while coming I think I would bite the bullet and get the tank off and inspect it.

Dont know which tanks are interchangable as I don't have access to a parts list, but hopefully someone else who has can help there.:(

[Russ]

Thanks for that,I was hoping gauge would be here today but it isnt.
I was wondering what can you see inside the tank,does the swirl pot go to the top of the tank or just rise a couple of inches from the bottom? As new tanks seem impossible to find I was thinking of replacing the pick up pipe (with the tank full of water) but i need to know if its just secured where it enters the tank .Then I would need some way of inserting a union in the outer skin and using copper pipe for a new pick up pipe ,but the problem is there would be no access to the inside of the tank.

Cheers
Russ

[G Force]

I was wondering what can you see inside the tank,does the swirl pot go to the top of the tank or just rise a couple of inches from the bottom?

The swirl pot is approx 4in tall and spot welded to the bottom of the tank. The pick up pipe is braized to the tank but I can't remember exactly if it is secured elsewhere, but I dont think so. The pick up is not easy to see but with torches and mirrors in the tank unit hole and filler tube you can just get an idea of the condition.

I had to cut into a fuel tank to find the problem with the efi I had eating fuel pumps because I could not see the gauze filter. It was a car under warranty and had had 2 new pumps fail. The problem turned out to be the gauze had a hole in it where it had melted. Obviously what had happened is during manufacture when the pick up was braized in place, the welding torch had been wafted over the outer end of the tube & the flame had travelled down the tube and melted the gauze. All it took to ruin the pumps was just minimal particles of rusty debris that had accumulated in the two years of running. Of course then I had to fit a new tank and another new pump.:)

Gary:)

[Russ]

I take it you were an austin rover mechanic then?
My plan is when i get the pres gauge,test the presure at the bus rail blank off the return see how long it takes for pressure to build. Then if still not satisfactory test the pressure between the pump and the pipe to engine ,if this is ok then the problem is in the pipe.
If still no good take the supply pipe from the tank off the pump and see how easy the fuel flows with a syphon pump. If its hard to syphon remome the tank (after draining) .Remove the sendor and clean inside tank,inspect pick up pipe repeat the syphon test with cleaner or water, if still no good remove pick up pipe and make new one from copper refit tank and come back crying on here saying my car still doesnt run right. Then get very drunk and walk off into sea!!!
Whats the best stuff for cleaning the tank and reducing risk of explosions?
Cheers
Russ

[G Force]

My plan is when i get the pres gauge,test the presure at the bus rail blank off the return see how long it takes for pressure to build. Then if still not satisfactory test the pressure between the pump and the pipe to engine ,if this is ok then the problem is in the pipe.



Hi Russ I thought it might be useful to summarise how you should test the fuel pressure, you might want to print it for referring to as you do the checks.

Connect the gauge in the fuel feed line between the fuel pump and the inlet of the fuel line. Depending on what adapters come with the gauge the best spot is T into the unions at the fuel rail inlet or you might have to T in just after the fuel filter. The gauge connections must be 100% secure and leak proof (fire warning)

Switch on the ignition and the priming period of 2-3 seconds should bring the rail up to full pressure in the rail (2.5bar) (approx 36psi). If you have lost a lot of fuel during connection of the gauge full pressure might not be achieved until turning off the ignition wait 15 secs and prime again.

You run the pump constantly by turning the ignition without running the engine by earthing the pink brown wire on the fuel pump relay if desired.

With the gauge installed you can easily see what the pressure is at idle (2.0bar) (approx 29psi) and with the vac pipe removed (2.5bar). If you briefly clamp the return hose the pressure should rise to approx 4.5bar, this tests the max output pressure of the pump; and no more than 6bar, if the pressure rises higher than this the fuel pump overpressure valve is faulty.

The Max fuel pressure test should prove any fault with the pick up as the fuel pressure should rise up to 60psi immediately once you clamp the return hose, any slight delay would suggest that the pick up is either restricted or drawing air or a pump problem.

You will also be able to rig the gauge up so you can see what is happening to fuel pressure when you’re driving, the pressure should never drop below 2.5bar when you accelerate or when under load.

You should also check that the pressure is holding in the rail when the engine is turned off. If it is not holding then clamp the return hose, if the pressure then holds then the regulator is faulty.

If the pressure still does not hold with engine off, then clamp the fuel feed pipe before the gauge, if it then holds the fuel pump non return valve is faulty. If the pressure drops with both feed & return pipes clamped off, you must have an injector leak.

Gary:)

[Russ]

Thanks for that Gary,The pres gauge still has not turned up:(
So cant really progress until it does,shame as its a lovely day down here.

How much crap normally sits in the tank? As it may be worth cleaning anyway

Cheers

Russ

[G Force]

How much crap normally sits in the tank? As it may be worth cleaning anyway


If it is the original tank I would expect there to be enough to justify cleaning it.:)

The tank that I cut up was only 2 years old and suprisingly there was enough silt to destroy 3 pumps.

[Russ]

Ive found a place in Norwich that will clean the tank and replace the pick up pipe for £40 ,ill wait until ive done the pressure tests before taking it down there. As there is still achance its the pipe from the tank to the engine. As the old pump was noisey and this one is not the queitest (compared to my metro which you can barely hear) does this mean that the pump is probably not full of fuel or its working too hard,ie trouble sucking from the tank or difficulty in forcing it up to the bus rail.

Russ

[G Force]

As the old pump was noisey and this one is not the queitest (compared to my metro which you can barely hear) does this mean that the pump is probably not full of fuel or its working too hard,ie trouble sucking from the tank or difficulty in forcing it up to the bus rail.

Russ

Tank clean & repair sounds promising.

If the pump was drawing air, then that would be one explaination as to it being noisey. The pump should be mounted with the large electrical connection uppermost for quietness. The pump gets noisey with wear also.

Gary:)

[Russ]

Cant find any suitable hose to rig up gauge for road test,however when I rev the engine the presure drops to about 15psi even with the vac dissconnected. The reg is working as the presure rises and falls with a vac pump operating the reg.
I still have to repeat the test at the rear but it looks as if the pump is being starved of fuel

Russ

[Russ]

Completed test at rear of car,just the same. Disconnected fuel supply pipe placed in jerry can and ran pump,I could P faster than the rate of flow coming from tank. Im suprised the car ran at all.
Drained and removed tank placed clean hose on pick up pipe and tried blowing down it seems very badly restriced in some way as I could not blow at all.
So,its off to the tank repairer in the morning and fingers crossed I may get it sorted.

Russ

[G Force]

when I rev the engine the presure drops to about 15psi even with the vac dissconnected.

Hi Russ; 15psi is way too low :) Don't want to jinx the project but I reckon you've sussed it mate;)

Gary:)

[Russ]

ITS SORTED!! :) Now drives like an efi should ,cost £20 in the end .A large build up of crud in the supply pipe,which was removed with specialist chemicals and steam. Not sure why it should have been there as the inside of the tank is spotless. A big thank you to all that have suggested especialy G Force.

Cheers

Russ

[G Force]

ITS SORTED!! :) Now drives like an efi should ,cost £20


Great news, glad you are sorted, :D

Gary:)