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I had a similar problem happen to me a good few years back. Ended up having to tow twice before I was able to isolate the problem to the fuel pump. I hadn't noticed the pump was overly noisy when it was running but it got to the point where the bearings in the pump were seizing when it got hot. Leave the car for a while and the bearings cooled enough for them to turn again. I know you mentioned in your first post that you feel the fuel pump sounded normal...but if the pump is struggling to turn and the FP drops below what is required for the car to run then you will have these same symptoms. Like you car, mine sat unused for many years and it was not long after getting roadworthy that the fuel pump went sideways on me. Just some food for thought.
Vapour lock? hat usually manifests itself after stopping whilst hot, no when cruising along but...?
Hmmm. Possibly. When it cut out the second time it was instant. No coughing or sputtering. My A/C does not work so the fuel cooler therefore doesn't cool the fuel. That would likely exacerbate a vapor lock issue I imagine. Would a failed or failing fuel pump check valve be effected by fuel temperature also?
Set up a few tools to carry around with you to narrow the problem down. When it dies again have a node tester to check injector pulse, and a spark tester to test spark. If your pump is running it is likely one or both of these issues. When you know what’s failing (spark or pulse) you have a diagnostic direction to go. There’s a bit of complex logic through a few relays that power the ecu and ezk.. lots of connections to fail too. if you study the diagrams you should find where the path to spark or pulse (or both) is breaking down.
Good advice. The more it breaks down the more reliable I am going to become in figuring out how it broke down in the first place.
Originally Posted by bronto
I recently had an issue with the fuel pump fuse not fitting tightly. The car never died on me but it did have intermittent starting problems. I discovered the problem when the fuse panel happened to be exposed, it was dark, and it wasn't starting. I noticed some sparking from the fuse panel, leaned over while the engine was cranking, and could actually see arcing around the fuse. I pulled the fuse, squeezed the connectors together the add some tension, put the fuse back in and it started right up. No problems at all since, it's been about 2 months.
Interesting. I will check all the connector tensions tonight. Thanks.
Originally Posted by drscottsmith
Almost sounds connector or solder related. The change in temperature could affect either. Continuity checks between components - but as stated earlier, that’s tough when you don’t know if the problem is fuel,fire or air related yet.
A bad solder joint somewhere in the ECU module would not be a surprise. Is the computer module connector firmly seated?
-scott
I haven't checked the fitment, but will do that tonight. Something like an expanding solder joint will be fun to try to discover if that's the issue. Ironically my lawnmower has the same symptoms as my 928. Runs great until it gets hot then dies.
Good advice. The more it breaks down the more reliable I am going to become in figuring out how it broke down in the first place.
Interesting. I will check all the connector tensions tonight. Thanks.
I haven't checked the fitment, but will do that tonight. Something like an expanding solder joint will be fun to try to discover if that's the issue. Ironically my lawnmower has the same symptoms as my 928. Runs great until it gets hot then dies.
Its like this Nate.... if you want to date the super model, you got to deal with her bullsh*t.
Its like this Nate.... if you want to date the super model, you got to deal with her bullsh*t.
Originally Posted by docmirror
Ignition keyswitch. Pretty common deal. If it just goes cold dead, check the ign asm.
Are these generally rebuild or when it goes is it just more prudent to replace?
Originally Posted by Lizard928
Pull the fuel injection relay and pop the cover off and see if it is going on or not. If it does not manually engage it and see if it starts.
Not sure if you saw, but the car started fine last night and I drove it into the garage. Since it seems like a problem related to heat, I am going to have to just get it out again and wait for it to die on me and then start the diagnosis. I'll be sure to add this one to the list. Thanks Colin.
84 doesn't have a CPS, that's basically what the green wire does. Unless he has a twin dizzy EuroS.
I doubt it's either, but I have a spare L-Jet brain and ignition box. Just say the word and they'll be on their way to Seattle. They are still bubble wrapped up and in a box from the last person that used them.
Originally Posted by docmirror
Ignition keyswitch. Pretty common deal. If it just goes cold dead, check the ign asm.
I'm starting to think of the ignition switch like the green wire, if replacement is unknown, do it before it fails since a faulty switch can cause all sorts of erratic issues.
When my fuel pump relay went bad, the car would start, then die. With some guidance of the guys here, I made a switched jumper that I keep in the tool box in the trunk now, along with 2 spare FP relays.
That's what I do for every 928!! Should be in the the toolkit!! haha
Nate,
The exact same thing happened to my '84. Turned out to be the coil. Easy to check the primary circuit. Coils get hot and then short out. Once cool they sometimes work again intermittently.
84 doesn't have a CPS, that's basically what the green wire does. Unless he has a twin dizzy EuroS.
Mine is a US model with a single distributor.
Originally Posted by Hacker-Pschorr
I doubt it's either, but I have a spare L-Jet brain and ignition box. Just say the word and they'll be on their way to Seattle. They are still bubble wrapped up and in a box from the last person that used them.
Erik thanks for the offer on the brain and ignition box. I'll shoot you a PM if the other checks don't bear fruit.
Originally Posted by Hacker-Pschorr
I'm starting to think of the ignition switch like the green wire, if replacement is unknown, do it before it fails since a faulty switch can cause all sorts of erratic issues.
Good to know about the ignition. I will definitely look into replacing it if for no other reason then to eliminate potential future problems.
Nate,
The exact same thing happened to my '84. Turned out to be the coil. Easy to check the primary circuit. Coils get hot and then short out. Once cool they sometimes work again intermittently.
Interesting. That would be an easy fix. It definitely behaves like the an electrical disconnection. Do you know if running an advanced timing could cause the coil to malfunction? My coil is a year old and before my TB/WP job last week I had been set at 23° BTDC with vacuum off the distributor. This time I went up to 25° to see if I could tell a difference in acceleration (oh yeah, very noticeable, much snappier). The owners manual for a US '84 model specifies 20°.
Well I took my car to work this morning. I haven't driven it since I drove it into the garage after the breakdown(s). Plus I haven't diagnosed anything since it will start and idle fine. Since the first two breakdowns happened after and hour and a half of driving in 70+ degree OAT, I figured a 20 minute drive to work on a cool morning would not be enough to replicate the issue. I was wrong. Breakdown number 3.
It drove great all the way to my work parking lot, then as I was reversing into my parking spot it died. Just like before. No bucking or sputtering. Just quit. Like before the fuel pump runs and it cranks strong, but it is not catching.
The first break down happened after I put the car in reverse as well. Is there some sort of switch in the gear selector mechanism that could be causing this? Driving it for only 20 minutes on a cool morning rules out a heat related issue, I think.
Rob mentioned that the FI relay could be replaced by the horn relay. Well I pulled the two and they are slightly different. As you can see the FI relay on the right has a terminal in the middle whereas the Horn relay does not. I switched them anyway and it didn't start. But also the horn doesn't work with the FI relay. Is that normal for a working FI relay? If not and the FI relay is bad, is the lack of the middle terminal on the Horn relay preventing it from acting like a proper FI relay? I also tried jumpering the 30 and 87 terminal and no joy.
Nate,
You could have a relay getting hot and consequently not working. Based on the history, let everything cool down, put the relays back in their original slots, and try to start it at lunch time. If it starts, great! When you get ready to drive home, prop your fuse /relay wooden cover open to that more air can get to the relays and cool them. Use an IR thermometer (if you have one) to determine which relay is getting too hot and then figure out why it's getting too hot. Good Luck!
05-07-2018, 03:11 PM
