Dying/No start ideas
12-09-2015, 10:57 AM
#1
Nordschleife Master
Thread Starter
Dying/No start ideas
I just finished swapping in a new long block to my '87 944. It's now giving some problems where it'll die when idling and not restart and refuse to start when parked running errands.
It seems to be affected by getting hot or hot-soaking. Twice it wouldn't start right away after being parked. The first time I had the wife come and jump it. It was cranking OK but with the boost it fired right up. The second time it started after many cranking cycles. After 6-8 tries it started to fire weakly and then die like it was flooded before finally catching well.
Lately it's died on me twice while stopped. It's gotten up-to-temp and then just dies like being switched off. The whole problem is likely electrical. The first time I got it pushed off the road, checked things for a minute with the hood up, and then applied a 3-wire jumper in place of the DME relay. Bingo! Drove it on home. This morning, I put in the jumper and drove it. Then it died after 15 minutes of running when I pulled to a stop. Wouldn't restart at all.
When I swapped engine I put in all the electrical parts off the previous engine. Everything from the flywheel sensors, AFM, idle valve, throttle body, injectors, ECU. The one part I left was the Temp Sensor II but I checked that in a cold garage last night. It gave 5150 Ohms and the old one gave 5250 so it should be OK.
It runs pretty well with just a hint of unstable running, maybe call it surging on occasion. It doesn't start running poorly and then die; it just dies.
Any ideas appreciated.
It seems to be affected by getting hot or hot-soaking. Twice it wouldn't start right away after being parked. The first time I had the wife come and jump it. It was cranking OK but with the boost it fired right up. The second time it started after many cranking cycles. After 6-8 tries it started to fire weakly and then die like it was flooded before finally catching well.
Lately it's died on me twice while stopped. It's gotten up-to-temp and then just dies like being switched off. The whole problem is likely electrical. The first time I got it pushed off the road, checked things for a minute with the hood up, and then applied a 3-wire jumper in place of the DME relay. Bingo! Drove it on home. This morning, I put in the jumper and drove it. Then it died after 15 minutes of running when I pulled to a stop. Wouldn't restart at all.
When I swapped engine I put in all the electrical parts off the previous engine. Everything from the flywheel sensors, AFM, idle valve, throttle body, injectors, ECU. The one part I left was the Temp Sensor II but I checked that in a cold garage last night. It gave 5150 Ohms and the old one gave 5250 so it should be OK.
It runs pretty well with just a hint of unstable running, maybe call it surging on occasion. It doesn't start running poorly and then die; it just dies.
Any ideas appreciated.
12-09-2015, 11:09 AM
#2
Drifting
What kind of DME relay are you using? If it's a Uro, you might have a problem with it. I've had them defective right out of the box. Most of us carry a spare and they're cheap, but get a reputable one. If that doesn't prove the problem, I'd be suspect of a fuel delivery issue. I'd recommend putting a fuel pressure gauge on the rail and seeing, first, what your fuel pressure readings are, especially the bleed down. Then put a hose on the end of the rail and do a fuel delivery test to verify how much fuel you're supplying. Also check the fuel hoses for softness to see if there's a collapsing issue.
12-10-2015, 12:25 AM
#3
Nordschleife Master
Thread Starter
What kind of DME relay are you using? If it's a Uro, you might have a problem with it. I've had them defective right out of the box. Most of us carry a spare and they're cheap, but get a reputable one. If that doesn't prove the problem, I'd be suspect of a fuel delivery issue. I'd recommend putting a fuel pressure gauge on the rail and seeing, first, what your fuel pressure readings are, especially the bleed down. Then put a hose on the end of the rail and do a fuel delivery test to verify how much fuel you're supplying. Also check the fuel hoses for softness to see if there's a collapsing issue.
It's failed on me with a jumper in place of the DME relay. I just put in the Rennbay replacement fuel lines. I'm not thinking it's bad fuel pressure as it runs pretty well and doesn't stumble at WOT redline combinations.
12-10-2015, 11:57 PM
#5
Nordschleife Master
Thread Starter
Ick.
Since I had to twist around the engine harness I'm thinking a broken wire somewhere. Or bad connector pin. Something like that. With it being intermittent, it'll be hard to find.
Then again, I just put it away for the winter and it'll be April before I get it out.
Maybe it'll fix itself and never happen again.
(too funny. I kill myself!)
Since I had to twist around the engine harness I'm thinking a broken wire somewhere. Or bad connector pin. Something like that. With it being intermittent, it'll be hard to find.
Then again, I just put it away for the winter and it'll be April before I get it out.
Maybe it'll fix itself and never happen again.
(too funny. I kill myself!)