Problems Starting

[SimonR]

I'm still having some problems starting my 1.6 Auto and don't really know how best to proceed.

The symptoms are that sometimes it starts and runs perfectly but at others it refuses to start at all, runs rich, runs lean (see below), idles too slowly, cuts out and won't re-start.

After setting the carb up as per Gary's instructions (with the venturi at the base of the brass bush) it started and ran quite well for a while until I drove it for about 30 mins, stopped it for an hour and then it refused to re-start. I thought it was flooded, but examination of the plugs revealed that it was running too lean and a half turn of the mixture screw got it started again.

Since then it has nearly failed to start again (eventually it did and then ran fine) then this morning, after behaving well all day yesterday, I got in it to go to work and although it started almost immediately, the idle speed was down to 500rpm, it smelt of fuel then cut out and refused to re-start, even though I backed the fuel screw off a little so that it was back to its original setting.

In the past, I've serviced the carb and inspected that all's as it should be, I can hear the stepper motor click on start up, it's got new O-Rings and there's oil in the dashpot. I've checked that the vacuum switch is operating correctly (can't suck air through it) so now I'm stumped.

I don't want to install a manual choke conversion because when the auto choke works properly it's very good indeed. I've never had this problem before on an S-Series car.

As a little aside, I notice in the green Haynes manual that in the section about tuning the SU carb there's a modification for the Automatic cars described and outlined in a picture, which seems to be simply removing the vacuum switch and joining the two pipes with a flexible hose. I'm wondering why this applies to the Autos and not the other cars....

[E_T_V]

The auto has a higher idle speed and is never really put in a situation where it must pull hard from low revs (due to the autobox), so it can probably make do without the restriction in the pipe and still get the correct mixture at high revs.

Check the autochoke ECU is connected properly (the end connectors are a bit dodgy sometimes). Also check the connection to the coolant sensor and indeed check that the coolant sensor is giving sensible resistances both hot and cold. An intermittant circuit here will cause all sorts of problems.

[SimonR]

Cheers Dan,

I shall measure the resistances on that sensor. Any idea what they should be when hot / cold?

I've re-seated the ECU a couple of times but am beginning to wonder if it's broken or has a dry joint somewhere...

I'll report back.

[SimonR]

Right, I checked the multiplug on the temperature sensor and it was quite dirty. I sprayed some switch cleaner into it, cleaned it and refitted it.

The readings from the temp sensor are as follows:

Cold: 3.38 K Ohms
Hot: 0.295 K Ohms

Seems to change, anyway!

I'll keep an eye on it and see if this has fixed it. Let's hope it has!

[SimonR]

Hmm, no such luck. My car doesn't seem to have a fast idle. When cold it's idling at about 500 RPM and obviously this leads to cutting out and general non-happiness.

I also notice that when I remove the coolant sensor plug, the revs drop almost immediately and it nearly cuts out.

I've reseated the fuel ECU multiplug and inspected it for damage. I may try substituting the ECU itself to see if this is faulty.

Could it be the stepper motor that's at fault? It makes the right sound when the ignition is turned on but I've not tested it to see if it's working properly.

How do you do that?!

Cheers, all.

[BikerGran]

I've had similar problems with Doris from time to time and it's usually been either some almost unnoticeable problem with one of the vacuum hoses (which I think I have at present) or, when I had the occasional petrol smell it turned out to be poor connection where the hoses are clipped onto the hard pipe, one pipe was perished - again you couldn't see the problem till the fuel was noticiably leaking - and eventually a leaking fuel pump.

[E_T_V]

When the coolant plug is removed the idle speed should increase, (or the idle speed increases and the choke comes one - it depends on which ECU you have). They shouldn't fall if things are all set up right. Is the mixture when hot correct?

[G Force]

Hi Simon R, sorry to hear you are still having trouble. I was just looking through what you have been checking as Ive been in London for the weekend.

First thing that I would say is if you checked the resistance of the sensor first thing in a morning berfore the car had been started at all, then the reading is quite a bit lower than I would expect and I would fit a new sensor. If you had started the car at all the day you tested it, then I would suggest rechecking it one morning before you start up to see if its any higher.

If you remove the coolant sensor plug when the engine is running cold on choke then you would expect the car to nearly cut out as it is just like pushing the choke knob in on a manual choke car.

Have you removed and cleaned the orfco valve to make sure it is completely closing the port furthest from the wires, and then disconnected it?

When I talk about setting the initial jet hight, this is a start point for adjusting the mixture by ear. I think in the faq bit I mention that in most cases this gives a slightly lean mixture. With the mixture slightly lean it makes it easier to detect the engine note change as you richen the mixture. It is far easier to get a more accurate result going from lean to rich then back a little, than rich to lean then up again, if you get what I mean:confused:

Cheers Gary:)

[SimonR]

Thanks for the replies Dan and Gary.

Dan - I'm not at all sure about the mixture now I've ready what Gary's just written. I'll reset it when I get home.

Gary - the instructions in the FAQ say:

Remove carburettor dash pot and clean with carburettor cleaner, observe the position of the main jet inside the carburettor venturi, screw the mixture screw until the top of the jet is level with the brass bush then screw the screw in one full turn. This should give a slightly rich mixture in most cases. Refit the dashpot.

Should that be lean mixture?! Also, the brass bush is bevelled. Should the jet be level with the top of the bush, or the bottom of the bush? See A and B in the attached image...

When I was checking the car before, I allowed it to warm up and then removed the coolant sensor plug. This resulted in the revs dropping and the engine nearly cutting out. I'll test this again tonight and report back.

I'll check the resistance after the car's been parked over night and possibly replace the sensor if it's no better. I'll also re-set the mixture settings when I know exactly where to set the jet.

Could this be a problem with the stepper motor? I ask because surely this should be mechanically operating the fast idle when I start the car from cold. Yesterday just as an experiment, before I started the car I increased the idle speed on the carb a good amount to see what happened. The car started off idling at about 500 RPM (I had to keep my foot on the accelerator to stop it cutting out) and as it warmed up the revs increased to 2,000 RPM.

Thanks for the answers, guys, I'm determined to get this damned car working!! It's so nearly there now.

[G Force]

Hi Simon the initial jet setting is as in A.

The instructions are right in the FAQ bit, it is my fault for not reading back what I wrote in the faq that is confusing you sorry.:o I forgot I had said turn the screw in one turn from the initial setting.

So dont worry stick with the faq instructions, and to avoid any more confusion, once you get it sorted I will explain what I was meaning in my last post, that seems to contradict myself.

If the engine is fully up to temp then disconnecting the temp sensor, should not cause the revs to drop, the revs should increase to 1200rpm if the settings are ok. Once you have reset the mixture would you check and reset the fast idle speed if necessary.

Gary:)

[SimonR]

Haha - Cheers!

I'm off to the car now with a screwdriver and large branch from a tree, just in case ;)

I'll also check the ORFCO valve.

[SimonR]

Righty-ho, hopefully I've sorted it with your help! I'll know in the morning I suppose.

I set the mixture as described and then got the engine up to temperature. Initially, unplugging the temp sensor made no difference so I inspected the ORFCO valve. It seemed OK but I screwed it back in and hey presto, now I get a 1200rpm fast idle when I remove the wire to the temp sensor.

How very odd.

If it's not working in the morning I shall buy and fit a replacement temp sensor and then go from there.

Thanks once more to you both for the advice. I'll report back if it's fixed.

[G Force]

Bloody orfco valves I have often thought if I had a car with one fitted I would super glue the rubber valve to its seat to prevent it ever moving. Just goes to show even cleaning & disconnecting the valve can't be relied on as the ultimate permenant cure.:banghead:

If you check the coolant temp sensor resistance first thing I would say anything above 5K ohms should be ok this time of year / weather.

Good luck in the morning:)

[SimonR]

GOOD NEWS!

I think it's fixed, or is nearly fixed anyway. It started and idled fine this morning, although perhaps the fast idle could be a little faster if I'm being a little picky. I'll adjust that I think and leave it at that.

Am I right that adjusting the fast idle is a case of bending the part of the throttle linkage that contacts with the stepper motor?

The resistance of the temp sensor was 3.6 K ohms this morning before I started the car so I found a spare sensor from the car I scrapped. This read about the same. I put it in the freezer for about ten minutes and the resistance rose to about 7K ohms.

What do you think, Gary - is it just warmer down south than you thought or are both sensors knackered in the same way? I wonder if a reading of 5K at the temp sensor would give a faster fast idle. If I can find some resistors later on (and remember the colour code!!) I may well test this. Failing that I suppose I could take the one from the freezer and use it before its temperature rises!!

Anyway, I think it's basically sorted so many thanks to all who helped. It will be nice to be able to rely o nthe car again because that's the whole point of having it!

[G Force]

Am I right that adjusting the fast idle is a case of bending the part of the throttle linkage that contacts with the stepper motor?


Hi SimonR, to adjust the fast idle you use the 7mm hex screw on the linkage nearest to the stepper motor jacking pin. the screw can be turned with the very small hex at its threaded end with a suitable mini socket if you have one. Some earlier carb linkages have another similar screw nearer to the cable this is the lost motion adjustment screw. You have to be careful not to adjust the fast idle speed too high as this can lead to running on when you stop the engine.


The resistance of the temp sensor was 3.6 K ohms this morning before I started the car so I found a spare sensor from the car I scrapped. This read about the same. I put it in the freezer for about ten minutes and the resistance rose to about 7K ohms.

What do you think, Gary - is it just warmer down south than you thought or are both sensors knackered in the same way? I wonder if a reading of 5K at the temp sensor would give a faster fast idle. If I can find some resistors later on (and remember the colour code!!) I may well test this. Failing that I suppose I could take the one from the freezer and use it before its temperature rises!!


I suppose it could be warmer than I think Yes. The operating range of the temp sensor is 30K ohms to around 100 ohms. As a general rule whenever I tested a sensor in free air in my workbay they would give an average reading of 5K ohms, so thats all I can base my thinking that 3.6K is too low on. Unfortunately I don't have a reference table of temp to resistance so Its hard for me to be realy accurate sorry.

The higher the resistance reading of the sensor the colder the engine temp, so more choke and fast idle is needed. If the sensor was reading low then the engine would not be given enough choke etc.

Even though we're not talking about massive malfunction, If it was me I would still be tempted to fit a new sensor if one can be obtained easily, just to rule it out. I realise its not me footing the bill though:laugh:

Gary:)

[SimonR]

Yeah, in the end I froze a sensor for half an hour and rushed it out to the car before it warmed up. The fast idle was perfect and the engine's revs dropped as expected as it warmed up in the engine bay.

I'll look out on eBay and buy a new sensor when I can find one. They're £20 from my Rover Parts place so a cheapy eBay special is the way to go I think. I like the challenge of running the Maestro on a shoe-string.

When it stops raining I'll nip out and take a look at that fast idle screw. I was reninded earlier of another job I've been putting off with this car for some time - I got in, drove down a hill and got completely soaked with water from the sunroof. I really MUST unblock those drain pipes sometime soon. :)

[G Force]

Just another word on the sensor, unipart sold two versions of the GTR 185 one had a One Piece body and one was a Two Piece body. Only buy a Two Piece type as the other was notoriously unreliable.

Cheers Gary:)

[E_T_V]

I'm pretty sure that the intermotor equivilent part number is 55150. Its common to almost all of the rover range, including 1.3, 1.6 and 2.0 maestros/montegos.
Cost is about £8 from a motorfactor.

[SimonR]

I thought I'd report back after a week or so.

So far the Maestro hasn't skipped a beat, it's started perfectly, not cut out once and is actually returning reasonable MPG figures now. It's also running so smoothly, pulling very well and not running on at all.

I think it's the first week that it's run properly for many years - I get the feeling that the reason it did so few miles in the years before I took on ownership was that it was so unreliable.

Cheers once more for your assistance, I finally have a decent Maestro again! It makes a huge difference to be able to get into it in the morning without a feeling of dread about my chances of getting it started. ;)

[G Force]

Hi SimonR, it is always great to hear that a problem has been resolved as it helps serve as a reference for others who might be experiencing similar problems.:)

It just goes to show that more often than not sometimes a problem can be caused by a collection of small defects, rather than just one single fault. I have to commend you on your perseverance and determination to get to the bottom of the problem, and rectify it in the way it was originaly designed to work. So many owners would probably have given up and either sold the car, scrapped the car, or fit a manual choke kit. Fitting a manual choke kit would have cost more and just masked around what was really causing the problem and not made the car run totally satisfactorily, so well done for not going down that route.:D

I hope that you can now have a long period of trouble free motoring cheers (looks round touches wood while squeezing lucky rabbits foot):D

[BikerGran]

Simon - did you fit a new temp sensor in the end? I ask as I'm having starting problems too, I thought it was down to one of the bends on the vacuum system that was splitting but I've replaced that and made no difference. Doesn't the temp gauge read wrong if the sensor is faulty?

[SimonR]

Simon - did you fit a new temp sensor in the end?

Bobbi - yeah I did. I had a brainwave that I'd bought one 'just in case' at an autojumble some time ago and a quick search in my spares collection revealed it, still in its original Rover packaging.

It has made quite a difference to the car.

The temperature gauge reading doesn't seem to have been affected by the sensor on my car.