Hi everyone

Just looking for some ideas to why my car keeps cutting out

So right after winter storage, at first start it sat idling for some minutes and suddenly just cut out. and kept cutting out when retrying.
A lot of testing and fault finding later and still no joy. although it has now developed so that it cuts out after 10 seconds - very constant
So I start the car and its starts just fine, runs fine, and then 8-10 sec later it seems to go lean, and just cuts out - the change from running fine to cuttig out happens very quickly. it begins to run lumpy for mayby 1-2 seconds and then it cuts out.

I have tried running the pump from another electrical source and it behaves excactly the same. Tried different pump, and also briefly without the fuel filter. Have tried blowing compressed air through the fuel hoses and it seems to be fine although I could be tempted to give it another go. because new fuel reg installed (went from adjustable to 3.5bar weber) and the fuel pressure is now 2,3 when the pump is priming - was 3bar before with adjustable reg. but it still behaves the same.

No sensor faults detected by IAW software

Have checked for vacuum leaks, but no luck (by pressing the throttle it just cuts out a little quicker, - had there been a leak I would have expected to be able to keep it running by pressing throttle)

I have changed
Fuel pump
Fuel reg
CPS
MAP sensor
imobilizer removed
relays for ecu and fuelpump changed

beginning to think it could be the ECU - but again it seems perfect looking at he IAW monitor on all sensors

grateful for any ideas

 

what car, what ecu ?

And the chances of the ecu being the problem...are almost zero.

Your description of the slow stoppage, sounds like the fuel pump is shutting off. So check power at the pump to see if this is the case just prior to it stopping.

 

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Sorry - Sapphire Cosworth 4wd
running an RP lab modified P8 ECU (which has been flawless btw)

100% agree on the fuel pump thoughts - but having tried all sorts of things I finally decided to put on another pump and run it from different power source - car behaved excactly the same.

But this time it died with the fuel pump still running obviously, whereas when fuel pump is powered normally by the car, it also stops when the car dies.

​​​​Have been thinking if something can be trapped in the fuel lines - but find it strange that it can start but not even stay running for more than 10 sec and that it behaves the same way - and if this was the case I would have thought the fuel pump kept running when it dies....

Thanks a lot for taking the time giving it some thoughts - at a total loss here

 

Again, keep it simple.

Fuel, Air, Spark...more or less.

Check 12v power to the ignition circuit during this period.

Check 12v power to the injector circuit during this period.

You say you've already ruled out fuel supply in terms of the pump. So check the other areas. Also, when it starts to die, are injectors pulse widths changing ? Or does it look like they are still trying to stay running ?

 

The fact it always cuts out, should make fault tracing easier than something intermittent.

Although if it is exactly 10s every time....it could be some odd control issue relating to say cranking enrichment, cold start, something ?

Do you have access to much ecu sensor data etc ?

 

Thanks mate

Yes - sounds so simple when stated like that
Good point on checking power to ign and inj circuits

I do have full access to sensor readings live on the RP Lab software and also error codes stored. All sensors seems to be fine.

Good point checking if the ecu tries to compensate just before it dies - will try checking that in the editor software.

Thanks again a big help and it motivates to have some fresh ideas- will report back when I have had the chance to test these things (unfortunately I cant work on the car before sunday.)

 

Not so much if it is trying to compensate...more is it actually removing fuel, or is timing going strange...or loss of a crank or cam signal etc.

 

Ok got it thx - not loosing crank or cam - because it flags no errors in the IAW when it dies

 

Well... Sometimes one have to admit when being an idiot....I believe to have located the issue.
When checking the pipe to the map sensor i did not check the small rubber connecting hose from inlet to the pipe. This hose was completely split...

So it very much seems that this could be the problem...
Will repport back when I have got round to start it up. Need to assemble the fuel system...
Talk about missing the obvious

Thanks Stevie for making me go back checking things already checked (sort off)

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It could very well be.

As Scanner Danner says...don't be a parts changer !

presumably with the split hose, your MAP sensor readings probably weren't doing very much when trying to start etc ?

 

I’ve always used the “spray easy start “ at it if I suspected air leaks or hose problems.
Well done In persisting with it.

 

It was not the split hose.... - I finally got it all assembled, and tried starting it but its still dying on me - 10 sec then shuts off
Tried to put some more fuel in to it on the fuelling table and that made it possible to keep it idling (badly) its misfire badly and a quick small push on the throttle and it cuts out.
So it could be that it still getts to little fuel to the injectors but manipulating the fuel table made them open enough to keep it idling.

I noticed a little electrical noise from the alternator when car is turned off. And that noise disapears if I unplug the ECU. Dont know what to make of that though.
Dammit

 

Again, look at what is happening at exactly that point.

What is timing doing, what are the injection pulse widths ? Are they doing something unusual that is leading to the stalling ?

 

Have you replaced the water temp switch / blue plug as I had big problems when my motor got hot . It could be that yours is doing the opposite . I might be Rong but as said look at the simple stuff . Check the air filter has not fell apart and is blocking the air to the motor .
you can just take off the air pipe to the throttle body and start the motor as they don't need a turbo to run . It's something to try

 

Thanks a lot for the suggestions much appriciated, understand its nearly impossible to diagnose at at distance

But a little progress - unfortunately not 100% sure what to make of it....

Let me explain
In the small window of 10 sec with the car running, I managed to add some extra fuel in the fuel table in the rp lab software to keep it running.
So by adding a small amount of fuel I think it compensates for the low fuel pressure I have discovered. The fuel pressure is only 1.7bar with vacuum hose on, and 2.3bar with it off. And it runs better with the hose off. So roughly I am missing 1.3 bar fuel pressure at idle (not even possible to raise rpm as it just dies the moment I touch the pedal)

Though I am pussled that missing "only" 1.3bar fuel pressure can cause it to be not running. would have imagined it at least could be driveable.
What do you think? Is it possible that missing 1.3bar can cause this?
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While I had it running at idle it showed no errors from sensors.

So I think that rules out a lot of things....
​​​​​The fact that it can stay idling by adding some fuel suggests to me that the ecu is ok, sensors are ok ignition system is ok. And I am back to fuel supply - or?

Earlier I did try and feed the pump from another powersupply and it behaved the same by cutting out. Then to me it seems it could be the pump on its way out, or the hose from pump to the rail.
But in the beginning of all this I also tried submerging the pump in petrol and it pumped lots of petrol through. When I almost blocked the outlet the pressure raised from it until the point where I blocked the outlet completely which made it almost stall. I thought it seemed fine back then?

If that test rules out the pump I am thinking it can only be fuel hose..
(the return hose fine as I can easily blow compressed air through to the tank)
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Hope it makes sense - what am I missing?
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Assume this is an external pump? Have you checked the tank outlet (to pump) isnt obstructed - seen bits of rust inside tanks partially block the outlets before therefore reducing flow/pressure significantly.

 

Yes Bosch 044 - everything from tank outlet up til the fuel line have been off - new filter as well

Good idea though
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Bit of a random one! My old Rs turbo had a immobiliser on it and it wen the battery In the fob was on its way out it would cos the car to shut off! Like an anti theft.
also the car would cut out sometimes due to the oil return being blocked , the oil light only flickered! Had the get it sorted and that cured the problem! Sorry if this doesn’t apply to you!

 

Thanks mate - imobilizer already removed as it was on the table at some point👍

No flickering and oil pressure is fine and stable

 

well thought it would be the right thing to just give an update in respect for those of you kind enough to offer some help and advise (and future searches)

Got the car sorted, and it was as expected a fuel delivery problem but with a few twists - I have been struck with bad luck, and some stupidity on my side.
So basically I had several errors going and at first thought it was somehow connected. Fuel pressure was low, map sensor reading was off., had CPS error at one point etc. So until I narrowed it down, I had been trough all sorts of fault finding on electrical system. Immobilizer, various relays, fuses, ignition switch, etc. etc.

But pressurizing the inlet system, found a crack in the hose to the map sensor, and data later showed map sensor was off. so changed hose and map sensor, but the fault was still there though behaved a little different now. Later I found that fuel pressure was a bit low, so ordered new regulator, only to find that it did not help - it was actually a little lower now.

Knowing I had new regulator new map sensor I kind of went on to other things to check - took fuel system apart blew through the hoses changed hoses checked fuel rail etc. etc.
Until as a desperate attempt, I ordered new fuel regulator again....now I got pressure. So all this fault finding, and it was down to 2x faulty fuel pressure regulators...the old one and the new one.
BUT still the fault was there, but now it was at least running better until the same point after 10-20 seconds where it would just cut out (not possible to keep it going with throttle - it just died)

then I tried loading a very old map file to the ecu, and now suddenly it would stay running - especially when warmed up. Though I had to adjust the idle screw to give it more air, as it otherwise only idled at 6-700 rpm barely.

So me being stupid is, that over a period of time (this is my theory) I think the small vacuum hose has got a crack that has gone worse, and also the map sensor has started to play up at some point (perhaps only a bit in the beginning).
Me not realizing this have just adjusted the fueling and the idle screw over a period time ever so slightly, thinking the map was bit off, and idle a little high.
I believe this is something that has been going worse over a few years. I have only driven the car about 500 km a year for the last 2-3 years, so I might not have been able to see the link of these things, when the car was not touched for months at a time.
So instead of realizing I had faulty components I had slowly adjusted the map and idle until a point where is simply would not run anymore - maybe triggered by a long winter hibernation.
Thinking back I was getting a bit annoyed as the car did not feel as fresh as I recall from years ago. But it cruised great and did go quite well when pushed, and given the lack of use I probably did not really notice it enough to realize something was wrong.
Thats it thanks for the input guys - really looking forward to the test drives the coming days...

 

Happy days mate, glad you have sorted the problem!! It’s the kind of luck I get,
I replaced everything and find out it something stupid 👍🏼

 

Glad you found the problem...... never easy when there are more than one.
Thanks for the update.