Diagnosis needed please.. Crank, spark but no start.

[FTO]

Hi guys, Im in a bit of trouble.
I bought a may93 vp 3.8 wagon (auto) a couple months back, and it drove really well for about 3 weeks. One day, during a short trip home, the car lost power under load, and was stalling upon idle (at lights etc). It broke down and wouldnt start again, and i noticed there was no pressure in coolant hose, so I added about 3-4Litres of coolant immediately. I should note that the temp gauge never went above half way. Car started again, and i almost made it home (about 2km) and then broke down again. I sat in the car waiting for it to cool a bit to see if it would get going again, but no luck. I walked home and returned an hour or so later. Started, and drove about half a km then broke down again. Did this again another couple hours later and made it the final 150m to my driveway.

At first iI thought, no coolant... ive cracked the head! FARK! I did a compression test and all cyl were fine. same readings all around, >120psi on first crank from memory. Then i did the basics, new fuel filter, plugs, leads. Still no fix. would start and run, then one warm, start coughing and spluttering, and finally stall, with no restart. I did a bit of research on this forum, and came to the conclusion it is prob the CAS.

I also discovered a pin-hole leak in my radiator, so I replaced it with a new one. Also put in new battery, bout 450cca. Over the weekend, i started the car, and it now only runs once for about 10 seconds, then stalls with no restart.

I got a new CAS and installed it on monday. After I put it in, started and ran for about 30 secs, stalled and no restart.

Back to the drawing board...
I went to pick'n'payless and got an ecm out of a 92vp wagon, and dfi and coils out of a 91 commodore.

First installed the coil pack with dfi and started. same thing, about 10 seconds of running with no restart.

then i pulled out my ecm and put in the new one (second hand) and tried... no start. then pulled out my original memcal, and put it in the new ecm cos the numbers were different, and tried that with no luck either.

Im stuck for ideas now... Whats the likleyhood its my fuel pump? Or do you think its a sensor of some kind?

I live in kellyville, sydney if someone wants to earn a bit of cash...

P.S I was getting diagnostic code 12, im guessing that if there was on picked up, it was lost when i put in the new battery...

Thanks in advance.

[drift-it]

i also had a prob like this in the vt, ended up being the ignition/coil relay, swapped it with high beams relay and i was sweet!

clamp off the return line and see if it runs for longer.

[FTO]

thanks, which one is the ignition/coil relay? Engine? the h-beams is 40a and the engine is 20a, will this be okay to test? when you say return line, you mean fuel right?

[drift-it]

yes fuel return line. as for the relays (not fuses) im not sure of the configuration on a VP. i know the vt had a fuse/relay box on the drivers side of the engine bay where the high beam/engine relays were kept.

[FTO]

oh sorry, relay, ofcourse, i was thinking fuse. i dont have 1 labled ignition coil, would it be efi?

[drift-it]

yer that will probly be it!...mine was full of burnt ants when i pulled it apart..

[FTO]

I switched the 2 relays, and tried to start, It turns over, but doesnt fire still. Thanks anyway Drift-it. Any more ideas

[drift-it]

bugger...ok i just found a efi manual, code 12 is system pass btw. for engine start then stall it lists 4 options, fuel supply, map sensor, coolant temp sensor and ECU. probably check in that order to.

[FTO]

cheers. any idea how to tackle this? im guessing i have to check/replace the fuel pump. Is it common for it to start and run once for a little while, then not start again if the fuel pump is wigging out?

[drift-it]

yer fuel pump would be my first suspicion as its an older car. easiest way would be to check fuel pressure and flow rate. and listen to hear the operation of the pump.

[FTO]

thanks mate. i'll try get my hands on a pressure gauge over the next couple days.

[FTO]

Okay, I tested fuel pressure before regulator going into injector rail and got 60psi on prime and no reading after regulator on return line... That's not right is it?

[drift-it]

did u check it while cranking and while running (if it runs long enough to check) 60 psi on prime is around 400kpa so that seems alright! you shouldnt get much pressure after the regulator as it just flows straight back to the tank, nothing to build pressure.

[FTO]

I didnt check pressure cranking, only with key turned to on. Another thing I noticed though was the vac line that comes off pressure regulator and goes to throttle body was full of fuel. Is it supposed to be?

[drift-it]

definitely not! sounds like the reg is shagged!

[FTO]

Okay, the car is going again. I changed the fuel dampened and regulator, unfortunately this still didn't fix it completely. I noticed that if I primed the car several times before starting it, it would run for a little while before stalling. Fuel pump wasn't pumping hard at all. So in with a new fuel pump and now it's all good. I pretty much have a brand new car now, haha. Thanks for your suggestions and help.

[drift-it]

good to hear its sorted!