79 930 Stalling Issue

Ccporsche · 07-02-2018, 01:14 PM

TL;DR: I've been having trouble with my 930 for a couple months now. It seems as though there isn't fuel getting to the engine at certain times. My mechanic tells me he's pretty sure it isn't the fuel pump. Anyone else had a similar issue?

Below is a rough chronology of the last 2 months:

-Took the 930 in for regular service a couple months ago. I got it back and a few days later it wouldn't start, however the engine did turn over.
-Towed it to the shop and the mechanic said he narrowed down the issue to a bad CDI unit. Had the issue fixed, drove home.
-The next day after I got it back, it stalled about 2 miles from my house. I had just turned a corner and as I shifted into second, the entire engine stalled (tach went to 0). Sat on the side of the road trying to start it for a few minutes. Finally got it started after 5 or 6 tries.
-Towed it back to the shop, mechanic drove it a few times before he had the same issue. Then narrowed it down to a bad fuel pump relay.
-Finally go back to the shop and pick it up last week. As I drive away I had a similar issue - I was in second gear, and it just lost power to the engine for a split second, I held my foot on the gas and the power came back. It was almost as if there wasn't fuel into getting to the engine in that split second. I then turned around to head back to the shop and it happened again as I was shifting.

I've owned this car for more than a few years now and this is the first time I've had any real issues.

kevinbodman930 · 07-02-2018, 01:25 PM

If it were me i would check to see if you have a loose wire on the fuel pump fuse bus.It could be that.I believe it would be the sixth set of wires at the front of the fuse box.It also could be that the fuse block has a crack and only is making contact some of the time.I had a similar prob and for the life of me couldn't figure it out,it was only when i went to put a new fuse in and it would not seat that i realized the crack in the block.Maybe the other pros can chime in.

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Ccporsche · 07-02-2018, 01:32 PM

Thanks for the advice! I'll check that out. Honestly, I'm not even sure if it is a problem with the fuel getting to the engine, just what it seems like to my amateur self.

Alan L · Alan L's Garage

The over boost switch on back of IC also fails - intermittently. Cuts the fuel pumps. Get the engine idling and wiggle the terminal on the o/boost sw. It is the white wire and white plastic housing on sw.
Alan

kevinbodman930 · 07-02-2018, 06:06 PM

That's a great suggestion you can also do the same for the wires that are going into and out of the fuel pump circuit.

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pkabush · 07-02-2018, 10:06 PM

Yep. I had an intermittent issue with the over boost switch. You can bypass it by running a wire from the switch to any good ground source IIRC. This will at the least, rule out the o/b switch if the problem persists. Good luck.

mark houghton · 07-03-2018, 05:20 AM

Quote:

Originally Posted by pkabush

Yep. I had an intermittent issue with the over boost switch. You can bypass it by running a wire from the switch to any good ground source IIRC. This will at the least, rule out the o/b switch if the problem persists. Good luck.

Just a little clarification: Running a wire from the switch wire to ground, not from the switch itself. The switch itself acts as a grounding point and if it's gone sour on you, it won't provide the necessary ground through the OEM wire when connected.

pkabush · 07-03-2018, 07:27 AM

Right. Thanks Mark. It’s been awhile.

T77911S · 07-03-2018, 07:28 AM

sounds like it could be the coil and the mech replaced the CD thinking he fixed it.

let it run at home, and get hot, and see if it cuts off. if it does immediately check for spark.
the heat could be killing the coil.

one other check, if it dies, leave the key on. go press down on the mixture adjuster and listen for the injectors to squeal.