OK, I'm guilty of neglecting/ignoring my 928 for a while-- its been in 'time out' for bad behavior. Now it has an intermittent no-start condition. The last work I did on it (aside from the exhaust) was replacement of alternator brushes, which required removal of the wire harness from the mounting point on the starter. I don't think thats related to my problem- my car will crank whenever the key is turned. However, seemingly on a whim with no correlation to weather conditions, and when not moved from the same stationary parking place, it will refuse to start. And when it does start and run at idle in place, after a certain amount of time-- typically 10-15 minutes, it will Occasionally die. It doesn't sputter and die as though its flooding or running out of fuel, it just dies like someone flipped a switch. Similarly, when it won't start, it gives no idication whatsoever of catching. I thought that it might be the fuel pump connections or relay. Howver, last time this occurred I *think* I smelled fuel after serveral seconds of letting the starter run (bad, I know but I was frustrated).
The fuel pump, filter, injectors, WUR, F/D are new or new used, as is the distributor, cap, rotor, green wire, and electronic trigger (TSZ box). And coil. Coil connections seem solid.
Can someone pls provide a primer on hunting down the problem, so I don't go on another replace-everything-on-unfounded-hunches kick? I really can't afford it! Thanks

 

These intermittent problems are a real pain to figure out. Try putting a light bulb(temporarily) on the power feed to the ignition box, and on + side of the coil. See if you can identify what circuit is losing power when it dies, then work backwards.

 

I don't know if this will help, but this advice came from the FAQ's at the top of the page...

"Intermittent Electrical Problems (86-95)

"When you first discover some part (s) of the electrical system is working intermittently, take a close look at the fuse panel. Pay extra close attention to any fuses that have been tampered with (i.e. Radar detector, cell phone or stereo connections). Pull each fuse out one by one and make a mental note of how hard it is to pull each one out. They should be almost impossible to remove with your fingertips. The ones that have a loose fit or are marginal, simply take each fuse out, using small needle nose pliers bend the legs in a "S"/"~" shape, then reinstall. This will force the fuse legs against the internal contact points in the fuse panel.

"If you still have a few problems, turn the ignition key to the on position, switch on what ever is not working and start wiggling and pushing in on the relays. If this works then you may need to replace a relay."

(I think this still applies to your MY as well.)

Good luck,

Phill.

 

Besides what has been suggested, check the connections on the green wire going to the coil. Also check the condition of the coil resistors (in front of wheelwell on right side) and connections. And last but not least, check/clean all of your ground wires.

Dennis

 

Thanks all. Resistors are new and the connections are tight. I'm really not wanting to get into a fuse panel rehash, but maybe its inevitable. Any other thoughts? I'm procrastinating by working on the Jeep DD so far....but I need to get the 928 running so I can get the paint repaired.

 

As a minimum, I would check/replace the fuel pump fuse, remove and reinsert the fuel pump relay and check the green wire connection that is near the jump post.

Dennis

 

The advice about bending the fuses into an "S" shape does not apply to your 83. For the early cars, try spinning all of the fuses in their sockets, and try wiggling all of the relevant relays. I assume you checked all of the green wire connections when you replaced it.

 

yup, checked greenie connections. Didn't make much additional progress today. One start/run fine, once wouldn't catch at all. Very odd.

 

Intermittent problems like this are almost always tracked down to electrical problems. Since it isn't heat related and you've checked/replaced most other items you should probably check for loose tension on the fuse holders and last but not least, the ignition switch.

Dennis

 

You need to monitor the various circuits... my bulb suggestion could apply to many other circuits and harness sections. It might seem silly to tap a bunch of bulbs into the harness, but it can be done without any damage to wire insulation, etc. and will allow you to watch several circuits at once.

 

Mm, ignition switch is an interesting idea. I've been procrastinating on getting another relay, I had a new one in reserve and swapped it in during a 'no start' episode, without any chance. I should keep one extra on-hand...and in the meant time Take Perf Products up on one of their (comparatively) cheap WURs...and maybe a fuel filter(gotta be number seventeen)...ah, here we go.

 

All great suggestions. I will add to them the suggestion to replace both your fuel pump and EFI relays (or temporarily jumper them). Usually, faulty relays will manifest themselves in a slightly different way (like a start-and-die condition for a bad EFI relay), but I will throw relays at most of these type of electrical problems as a very cheap and hassle-free first line of offense. The relays do tend to flake out over time anyway and should be replaced as a matter of course.

On my own '83, I have had both the start-and-die problem as well as the crank-no-start problem. The former was a bad EFI relay and the latter was caused by faulty ground points. The great thing about the L-Jet system is that it is almost bulletproof, the hardware almost never fails, and diagnosis is not all THAT bad (though you probably don't feel in agreement with that latter statement at the moment!!)

Good luck and let us know what you find!!

Rick

 

haha EFI relays, good one!
This is a Euro, so its K-Jet.

I did just find a parts listing for an intertial shutoff switch for a '79, but I think that was an erroneous listing.

I was just out with it, started OK, ran for about 5 minutes. I got in to lift the rpms to 2400 for a little while-- could tell the alternator got into gear at that point with the lights brightening! After 30 seconds or so I could hear something change markedly, then my A/F meter went lean. THen it died. So although it wasn't clear to me in that instant, I think the change in sound was the fuel pump shutting off. Back to square 1. Its a rebuild with only a few hundred miles on it, but it has spent a good amount of time sitting in-between, its about two years old. The relay is a virtual certainty (sixty bucks, grrr), I'm less eager to plunk down for a pump until I isolate that as the culprit.

 

Sucked it up and bought a new pump...stay tuned, I guess.

 

I have had this or a similar condition on the '85. Happened last two times (weekends after the car has sat in heated garage for 2-3 weeks - gets a little damp in there). I crank for 6-8 seconds stop. Wait 30 seconds. On the 4th try, it starts, runs 15 seconds, dies cleanly. Wait, crank 10 seconds, it has a different breathy sound, turning easily, like there is less compression (could this be a partial fire from fuel pressure coming on line?), but then it starts, keeps running. Later and next day, no hesitation. If it happens again, I'm checking relay and grounds, check valve, fuel pump. the filter was changed a few thousand back. ISV is new and vacuums were replaced.