Hi, long one sorry! HISTORY I stalled it on a hill taking off in first, I was surprised just how violent it felt. Car was running slightly rough when cold last few weeks since roughly then, once warm was OK my MPG was around 18 mpg, I changed the blue temp sensor even though old one tested OK according to resistance values at various temperatures using a laser thermometer. My MFA MPG values have been null since I bought the car, I ordered a new hall sender based on Rubjonnys advice for speedo to deliver distance info to MFA computer (the fuel usage value was displaying as a number between 0.6 and 6 I think, vacuum line based so just needed the distance). I have made some videos, a kind of how to, if it works I will share to the club. Car harness is generally in excellent shape, very little wiring butcher work (apart from radios). I have removed all traces of alarms and immobilisers, soldered all cables and heat shrunk them. When I rebuilt dash the car wouldn't start. You hear the HP fuel pump prime for a few seconds. I did not disconnect car battery before having the dash out, I cannot see how that could fry something in the ECU. What I have tried 1. I was not too rough with cables. I looked in engine bay and scuttle to ensure movement of speedo drive and vacuum hose to MFA had not damaged any other wires. Vacuum line is good with suck/blow. 2. Tested ECU, X-over and fuel pump relays, all fine. 3. I bridged 30 to 87 on fuel pump relay, I heard the fuel pump in tank running. 4. Confirmed 12 volts at injector rail positive and confirmed connection from switched ground from ECU to injector rail. 5. Cleaned various sensor wires with electro solvent. 6. Cleaned ignition module on top of ECU with electro solvent. 7. Cleaned ECU pins with electro solvent. 8. Split connecter beside ECU and cleaned pins. 9. Confirmed ISV buzzes, then Soaked ISV in WD-40 for 5 mins, blown dry with air duster. 10. Lowered fuseboard looked all around the area for disconnected wires, none found. 11. It has a decent white spark at all four plugs, I wire brushed plugs to clear carbon deposits. When cranking plugs out fuel vapour I believe. 12. I put in an extra gallon of premium unleaded. 13. Charged battery. 14. I put my timing light on and confirmed spark on cranking. I have read that weak coils cause all sorts of troubles and i'm actually thinking to buy one? 15. As i had a spare distributor known working, I changed that anyway, ensured flywheel punched dot (piston #1 TDC) aligned with OT on cam and plastic covers. Rotated crank to line up flywheel slash mark, set distributor rotor centre to distributor indentation on housing (6° BTDC) and rotated crank again confirming all correct. 16. Its an 8 valver so rotor arms turns clockwise. Put cap on, rotor at #1, HT lead to cyl #1 (cambelt end of engine). Lined up my HT leads 1, 3, 4,2 clockwise. 17. Tested throttle switches, seem to cycle normally closed, mid throttle, normally open, full throttle normally closed. 18. Tried using a new ignition switch. 19. Opened bleed nipple on fuel inector rail, fuel there. 20. Checked resistance of all four injectors at once, 4.5 ohms (manual suggests 3-5 ohms all four). It has ran briefly, very roughly yesterday, so I turned it off, hasn't started since! I'm at a loss! not tried to clean throttle body yet. I do have a spare ECU but I have not tried that yet. I would expect it to fire even roughly with fuel and spark? Any help greatly appreciated.
does fuel pump prime on ignition and run while cranking? next thing I'd look at is the pins on AFM, make sure tight and fully pushed in, pull rubber boot off the back and check wires to the back are ok. you can check afm itself with multimeter, deets here: https://clubgti.com/forums/index.ph...ose-and-tune-your-mk2-digifant-gti-8v.124949/ also go over all the inlet boot, breather rubber bung etc for cracks as per my guide but a small air leak wouldnt cause this I don't think. mine used to cut out randomly it turned out the fuel pump fuse on the fusebox was burnt so it would breifly loose contact so thats worth a checkover. ECU relay also worth a look, you can bypass like this:
Hi Jonny, thanks for the detailed reply. The AFM wires are intact. The fuel pump always primed, however I have not confirmed during cranking. I removed relay from slot 3 (32 ECU RELAY) and bridged pins as suggested This wakes up the ISV as it buzzes, but you do not hear fuel pump prime (not sure if I should as no key turned yet). When you turn the key to IGN on the fuel pump does not prime (usually it does with relay 32 in place), I then proceeded to crank it over, sounds like it wants to catch/fire up but doesn't. When you return key to IGN on position you hear fuel pump running then it stops ( the under car pump you normally hear priming). My new ignition switch is hanging loose just now and i'm using a screw driver (hopefully this does not need grpounding to column etc.
repeat the tests but with ignition on first, the fuel relay needs an ignition live to it to switch so you probably just missed the 'prime' window after doing the jumper and moving on to turn the key from what you describe though I think you're good on that front
Hi Jonny, I turned key to ON then jumped ECU slot 3 pins and sure enough fuel pump primed. With all I have said do you believe ECU is OK or change anyway? Tomorrow I will get a helper to listen for pump running during cranking. Also I will clean throttle body and looks again at all air side ductwork. Thanks.
Put battery on charge. I can smell fuel at exhaust when cranking, just wont fire. (I checked my sump oil and the level is slightly up!!! has petrol gone to sump by flooding? Removed throttle body today, cleaned it as it was dirty. The rear usually plugged vac line was missing and I thought great... but the line was choked with dirt, I cleared it and fitted new vac line blanked. One knife mark in the hose between the crankcase breather to throttle body hose, taped up for now. Vleaned crankcase breather, very clean. Perhaps mesh below has gunked up? Tested AFM pins 1-4 (air temp sensor) read 3.5K ohm which by chart was correct for todays temp. Tested AFM pins 2-3 and swept stylus anti clockwise, the resistance fluctuates but not as expected (now if car is cranking over this would be at an idle rpm equivalent percentage open). I expected the fluctuation to either be increasing or decreasing depending on direction of movement, it seemed to build then drop turning anti clockwise which makes me think i'm connected to wrong pins. I removed vac line from FPR, no fuel there, that is good. I connected a new line and sucked on it and blew it, all good there, no issues with FPR diaphragm. Vac line to upper airbox (flap function) seems like you can suck on it forever, my belief is car needs to be running to test this. I may just temporarily block this to rule it out. I think this will be 'open' until car is running that way flap can spring shut. Lunch over, taking off charge and going to see if it starts. Any ideas?
Not starting, runs for a second or two then dies. I checked ECU pins to AFM, all four are good. Going to order a coil and a fuel filter, try filter first. Any ideas?
God this one is a ballbreaker It is worth changing the fuel filter for sure especially if it's been in there for a while - they can gum up and cause issues. You have already confirmed a good spark so not sure if changing the coil will make a difference - can you get your hands on a second-hand one just to try that first before forking out for a new one? When did you remove the immobiliser - was that before or during the dash removal? If it was during then are you absolutely certain that all traces are gone and there isn't anything left holding the car back from starting? I keep going back to the fact that the car was working (albeit drinking juice) before the dash came out - have you checked the fuseboard connections at the back in case any became dislodged during dash removal - long shot I know but worth a look.
Hi Costel, thanks for the reply. God this one is a ballbreaker agreed It is worth changing the fuel filter for sure especially if it's been in there for a while - they can gum up and cause issues. I filled tank for the first time a week ago to determine mpg, car has been running rough since around that date so fuel filter could be a good shout incase plus the car is 34 years old so good practice When did you remove the immobiliser - was that before or during the dash removal? If it was during then are you absolutely certain that all traces are gone and there isn't anything left holding the car back from starting? 2022 I removed immobiliser and alarm. I re-joined all wires with solder and heat shrink so you would think they are solid I keep going back to the fact that the car was working (albeit drinking juice) before the dash came out - have you checked the fuseboard connections at the back in case any became dislodged during dash removal - long shot I know but worth a look. I have lowered the fusebox twice, the multi wire blocks are all still in place. Various optional extra single tails are loose but I have not gone into any detail to see what they are for, in my opinion, the important cables are the multi plugs and they are kind of locked in anyway by that long plastic horizontal locking interlock bar. To be fair, the wire that goes to the fuel injector positive is a Z1 or so and it can easily come out. That one was chopped and used for immobiliser which i have since soldered in 2022 and buzzed this week to ensure no dry solder joints etc. I am going to start at fuel tank and trace the petrol to the engine/injectors. I'm fairly useful with tools and electrics but I do make mistakes, so rest assured if i've done something stupid I will come back and explain just to close out this thread. I love driving this thing, i'm out of work at the moment so I go for a 40-60 mile blast every few days, but with it drinking fuel and no work perhaps the petrol saved is a good thing! Cheers, Garry.
Sounds like a plan Garry and I do hope a new fuel filter will stop the ballache. The drinking petrol thing would need a look when the primary ballache is sorted - they are pretty good on fuel all things considered so the mixture and AFM might need fettling. Cheers Robert
Check fuel pressure at the engine Also, there's a multi plug close to the ecu, corrosion there caused a similar issue with a mates car. This violent stall... I wonder would it have jumped a tooth on the cam belt? Worth checking.
Hi Tristan, thanks for your reply. I had read about stalling and jumping a tooth on cam sprocket, so I checked the cam shaft markings and they align with the OT stamp on plastic shroud, and the flywheel TDC #1 punched dot remains aligned. Car did run for a while after the stall so I think its all good, now I just hope the key or whatever hold sprocket to cam has not sheared but I'd doubt that would happen. Fuel checks from tank to injectors are todays jobs. The multiplug beside ECU and TCI ignition module have been checked and cleaned, some wires buzzed with multimeter. Thanks. I will report back later.
the AFM test doesnt sound right, it should give a resistance curve as you move the flap from your description I wonder if theres something up with the contacts inside... put it on the list of things to check anyway. All my 8v bits long gone so I cant compare a know good one, hopefully someone can help out with that. also worth pulling all 4 spark plugs out for a clean up, and just leave it for the residual fuel to evaporate. injector test might be a plan also, it could be the ecu has popped a component inside and is just flooding the engine, usually when they go it also puts the fuel pump on constant but not always
Hi Jonny, thanks for the info. I cleaned carbon deposits off spark plugs two days ago. AFM, i cleaned resistive arcs with electro solvent, maybe i will use a cotton bud and electro solvent this time instead of simply spraying. Then re-test resistance which seemed odd to me as it wasn't a continual drop or rise which I would expect but I don't have info either on how that resistance should read, I thought the stylus should just be 'parked' at one position on the arc for idle. I just replaced fuel filter under car, what I expected to happen was the line from the tank to filter inlet to dribble until I stuck new filter onto that line, it only seemed to drain 'line volume' now I would have thought the 'in-tank pump' which works to allow fuel through it like a centrifugal pump, maybe i'm wrong and it is a positive displacement type pump. Now the strange thing is the car tries to fire up every few engine revolutions and the rev counter needle 'jiggles' when firing only. I would have thought during cranking the as the tachometer is fed from coil wire it should be recording a rpm needle movement all the time? I was going to go through the fuel system today but its raining so im just going to try the spare ECU next. and go over all the under dash fusebox area old splices re-soldered incase something is wrong. Thanks again Jonny!
Busy thread getting... looked into some aspects of what's being talked about donkeys years ago. Most of it's very hazy now, so won't throw out half remembered pointers and send you off on the wrong track, read this instead - https://www.clubgti.com/forums/index.php?threads/stuttering-under-load.292197/ May or may not be stuff in there that's relevant, but could provide some places to start your own enquiries from. Potentially interesting first post, some commonality with / causes / consequences of your own hard stall perhaps? Difficult to see in your video... are any of the traces on the board badly blurred, the little black squares and rectangles? Can be an indication that they're no longer good, need to keep moisture out of there at all costs.
I dont like the look of those readings on the afm but as I say I dont have one to compare so cant say for sure... certainly if you take the pipe off the bottom of the reservoir, the entire fuel tank will eventually drain by capillary action, burt with the fuel filter I guess the main pump will stop too much fuel coming through as its pretty tight tolerances inside when cranking you should get a consistent spark and also rev counter jiggle, potentially this is linked to the odd readings from the afm
In that case I should remove that filter inlet hose again and see if it drains continually. Then run in-tank pump only to see if fuel is delivered by in-tank pump. If not, then I should pull out in-tank pump and see what is going on. Thanks very much. I installed a new electric garage door this afternoon so that put a big smile on my face instead of getting nowhere with Golf.
