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!tom · Posted: Sat Sep 02, 2006 3:33 pm Post subject: It keeps on shutting off!

Portions of this I'm sure are in various FAQ's, but perhaps I could get some help troubleshooting.

Twice now it's died while driving. I initially thought the coil wire from the coil to the distributor worked loose, but I managed to do a bit more investigating the 2nd time.

When I grounded the thermo-time valve as described in the warm start problems FAQ, the engine would fire and run for a second or so, so this ruled out the ignition and got me looking at the fuel delivery. While cranking, the fuel pump was not running. The fuel pump looks relatively new, and it's mounted using a flat head wood screw behind the rear tire well, so I don't think it's an original part. I poked it a little bit when I was looking at it. Since I had just gassed up about 2 miles ago, I was wondering if there was a vaccuum in the tank, so I took the gas cap off. Then, the car started on the next try, and it brought me home.

So, I'm still not sure what made the car start to work. It could have just fixed itself by sitting for a few minutes. Or, there could have been some sort of vaccuum in the tank preventing fuel delivery. Or, perhaps there is a probelm with the fuel pump. However, if it were a fuel pressure problem (vaccuum or faulty pump), then how did grounding the thermo-time valve get the car to fire when it wouldn't fire without grounding it? I would expect there would need to be fuel pressure to get that to work.

Is the fuel pump supposed to run whenever the key is turned to "on?" Or is it supposed to be like my other vehicle and shut down when it's pressurised the line?

Any tips? It's done this twice now in the span of three or so weeks, and I have no clue how to bring it on.

leadfoot · Posted: Sat Sep 02, 2006 4:48 pm Post subject: Re: It keeps on shutting off!

Ozzie · Posted: Sat Sep 02, 2006 6:26 pm Post subject:

There are lots of threads about fuel pumps and relays.
If you do a search you'll find a lot of info.

The pump is controlled by the ign and pump relay.
When starting/cranking it will run but shut off if the motor doesn't fire.

Sounds like a pump relay fault to me.
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924RACR · Posted: Sat Sep 02, 2006 10:30 pm Post subject:

Agreed, I'd be suspicious of bad relay, wiring, or pump in that order.

You can make up a big jumper for the relay, carry it around with you, and next time the car dies, pop that in and see if it'll run again.
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!tom · Posted: Sun Sep 03, 2006 9:13 am Post subject:

Well, I was planning on just replacing the relay for the fun of it, but the parts guy wasn't exactly sure if the cheap option would work, and the cheap option sure sounded expensive to me!

I pulled the old one so that we could compare, and there's a manufacture date of September of 2004 on the old one.

So, it's probably not the relay.

He mentioned something about a remote mounting kit for the relay since they tend to overheat. So, at this point in time, I've done nothing.

dpw928 · Joined: 02 Nov 2002 Posts: 1860 Location: owasso, ok 74055

Intermittant electrical problems are normally associated with heat buildup. The most likely places are the fuse contact area (small), relay contacts and grounds. Have you checked the fuel pump ground in the hatch for corrosions?

Dennis
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D Hook · Joined: 02 Nov 2002 Posts: 3158 Location: Omaha, NE

I wouldn't rule out the relay just yet. Do you have a spare you can swap in? Or do the jumper trick?
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!tom · Posted: Mon Sep 04, 2006 1:20 am Post subject:

The relay was too pricey to get another one "just in case." I'm more suspicious of the fuel pump; it sounds like it might have a bearing on the way out, or something like that.

The problem is that this is my wife's car, and she's not going to be happy with the idea that it might just die with no warning. And, since the problem seems to just go away by itself, it's going to be very difficult for me to be convinced that I've actually fixed it! I still can't reproduce the problem, so I have to be prepaired to troubleshoot on the road next time it happens.

I'll make up a jumper wire.

So, when using this jumper, does it turn the fuel pump "on" so that it is continuously running? I'm anticipating having to troubleshoot this myself on the side of the road. If I put the jumper in and the car doesn't start, should the fuel pump be running with the key left to "on?"

dpw928 · Joined: 02 Nov 2002 Posts: 1860 Location: owasso, ok 74055

When you jumper sockets 30 and 87 the pump should run regardless of where the ignition key is located, so just leave it jumpered long enough to test it.

Dennis
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OutOfTheBox · Joined: 31 Mar 2006 Posts: 434

Make up a jumper wire.

Remove the relay and jumper the contacts.

Switch ignition on, and check fuel pump is running.

Go to fuel pump, and try "poking" the connections and earths, and check it doesn't miss a beat.

replace fuel relay, and keep the jumper handy

next time it wont starts, repeat the above.

If it then starts fine, your problem is the relay.

If it was my wifes car, I would remove all the connectors from the back of the fuse box and clean, as well as the fuseholders.

D Hook · Joined: 02 Nov 2002 Posts: 3158 Location: Omaha, NE

teo · Joined: 07 Sep 2001 Posts: 637 Location: Hungary, Europe

Ignition switch (on the steering column)?

I had a contact problem with the ignition switch, symptoms are the same, it dies while driving, you check things or not, then it starts without reason.
Of course you move the key in the switch, so contact is back, then it does it again some unexpected time.

Just a thought....

!tom · Posted: Mon Sep 04, 2006 12:13 pm Post subject:

A couple points. . .

I can't remember the price exactly, but I seem to recall something on the order of $70.00. Seems quite pricey to me for a relay. That's when I realized that I had an essentially brand new one already.

I don't think it is the ignition switch like you describe, because the darned thing wouldn't start 'till about 10 minutes of fiddling, and probably 15 or 20 starting attempts. Mind you the key wasn't removed every time, but it was fiddled with in turning it from "run" to "stop" to "start" every cycle.

Like I said, I'll make a jumper so that I can rule out the relay, and I'll bring a voltmeter with me as well.

Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

924RACR · Posted: Mon Sep 04, 2006 10:44 pm Post subject:

Tom, do you have a turbo? Those have a rather pricey fuel pump relay, not to mention some classic problems in the fusebox with overheating due to corrosion.
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'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype