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-   911 / 930 Turbo & Super Charging Forum (http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/)
-   -   930 engine shutting off (http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/324733-930-engine-shutting-off.html)

flatboosted 01-13-2007 06:17 PM

930 engine shutting off
 
Problem with my 78 930..the engine shuts off between shifts, just like you turned the key off, then after a few moments comes alive again. This problem started a few weeks ago as infrequent, now it is becoming very frequent. Under boost it runs like a goosed goose, no problem there, it seems a bit rich though, particularly at idle where it will burn your eyes. It has been that way for a long time, i don't think that is a contributing factor. This problem seemed to happen all at once. Seems when you lift your foot off the gas, the engine shuts off, hit the key and it starts right back up, seems like it runs out of gas?? Both pumps are new and run fine.
The car had a recent major done , everything rebuilt or replaced, usual upgrades, Powerhaus IC , K27, 1 bar spring. Euro spec car 700 series number. Ran terrific for the last 3000 miles since.
Anyone have any ideas where to start???

gsxrken 01-13-2007 08:29 PM

You may have a loose engine or transmission ground, and when the clutch is depressed something is getting grounded. I think I remember Stephen at ImagineAUto posting about this once.

You might also be running into the infamously flaky yellow relay, the tall one on the tray in the engine compartment. Yours might be the original one, almost 30 years now, and littel solder joints fail inside. When this thing flakes out, it cuts out your pumps. Then it jiggles or cycles or whatever and your pumps run again. Try searching on "yellow relay" and see if the symptoms ring a bell with you. GOod luck and welcome to Pelican.

NathanUK 01-15-2007 08:26 AM

The yellow relay might also be a red or black relay in its place.

flatboosted 01-15-2007 02:13 PM

Gents, thanks much for stimulating my brain , it was the relay on the engine compartment tray. Must have been some corrosion around the pins, a shot of WD-40 and cleaning the ends of the 3 fuses below it fixed the problem.
Off to the races...

jwmarc 01-19-2007 01:43 PM

I agree it could be the yellow relay ...pull the cover and inspect the solder welds... I re-soldered those that had cracks... never had the issue again... Thanks to john walker!!

vmb 01-21-2007 04:53 PM

perfect timing for this thread! My motor shut down on me last night on the freeway, (in Columbia, jwmarc!) and I can't hear the fuel pumps w/ the ignition in the "on" position. The front fuses and relays are OK. Where exactly is this yellow relay in the engine bay?

(And a big thanks to sdubovsky for the ride home, and offers to tow later)

flatboosted 01-21-2007 07:19 PM

the relay is on the tray in the engine compartment, drivers side .The tray or shelf should have a cover over it with a thumbscrew holding it on. Once open you can't miss it. It could also be a red or black relay just like the fuel pump relays in the trunk. Good Luck, its always a good idea to carry fuel pump relays in the glovebox, sure beats walking

jwmarc 01-22-2007 05:04 AM

The yellow relay is on the left hand side facing the engine.. There should be a cover over a number of electrical components (Back of cover says what is there). The yellow relays cover can be pried off....be careful.... Look at the PCB and in particular the main prongs which seat in the connector.. as the prongs go through the board look at the top side where the solder covers the pin .. if you see a faint dark circle the solder has developed a very small crack and when it heats up can expand enough to trip the relay. This is a non-standard relay..ie a printed ckt board with internals which activate very fast and have very close tolerances...it is there to protect the engine from over-boost and provides the "momentary" cut-off of the fuel pumps.

Sometimes if you flick the relay body with your finger it will make contact and work... The first stall I had I did this trick to all the relays... front and back.... and the car started.

John Walker who is a shop owner and contributor to this board was the source who advised me when I first purchased the vehicle and had the stalling problems....

Re-solder the prongs..but be careful about the heat you use...you don't want to fry anything else on the board.

BTW if you don't have the yellow relay ...there may be another standard relay-- Red or Black round one. Try substitution...

Also you may find the car starting right up after it has sit for a while..

Good luck.

vmb 01-22-2007 06:11 AM

so, is there are difference between the red, yellow, and black relays? I can find red and black replacements online, but no yellows.

jwmarc 01-22-2007 06:17 AM

The difference is about $150+....

the red and black are standard relays... mechanical coil for high currant switching... costs about $15-$25.

the yellow is a very expensive integrated circuit relay.... with mechanical contacts. It is specific to the turbo and its application for fast switching...

pelican sells it.. but you have to call them and tell then that is what you are looking for as it is special priced and ordered.

NathanUK 01-22-2007 01:42 PM

Might be a stupid question, but...

Can a yellow relay be replaced with a red or black one ?

jwmarc 01-22-2007 04:22 PM

I dont believe that they are able to be substituted...The yellow relay has a more sophisticated electonic design...ability to switch faster (process the input control signal- voltage). The other mechanical relays have a slower response time to perform currant switching... the system design could be compremised if the appropriate relay isnt used....also the connector form factor would need to be modified.....

Kimos 01-27-2007 09:47 PM

Ditto . . . perfect timing. My 930 track car just died yesterday (&@^$^%&@#$. I decided to stretch her legs and went out for a spin. Let her warm up and all OK, Everything was fine and then she just died at a light as if out of gas. After a few trys she finally fired again and drove home. However, once back and prepping to park she died again but now she wont start. New engine few months old and no previous issues. Checked air/vac lines, fuel pumps, fuel and have fire at coils (12 Plug system) overboost switch? relay? Any help greatly appreciated . . . .driving me nuts . .
BTW I dont have a yellow relay. Can someone send an image of the exact slot? Perhaps mine was replaced with another type/color

Kimos 01-27-2007 09:55 PM

I checked the relays. I have a red and a black. The red is just above the fuses and the black is further back. Engine professionally built anf no previous issues.

If the relay flakes out how does it kill the engine? Prevents firing how?

vmb 01-28-2007 05:14 AM

I checked my relays yesterday, I have a red one in the engine bay, and all black under the hood. I swapped out the red one for a black one, and got a slight sputter, a little smoke from the tailpipes, but no susteined firing. Interestingly, I got the same result with no relay at all in the engine bay slot. And I never did hear the fuel pump(s) buzzing.

So, I'm going to order a yellow and a red relay, and hope that this solves the problem. Unless anyone thinks that I may have a primary fuel pump problem. Any thoughts? Thanks!

One other thought- if the more sophisticated yellow relay is so important for engine protection in the turbo motor, is this something that future potential buyers should know about in evaluating a possible purchase? Will a non-yellow relay in the engine bay carry a higher risk of motor damage? Perhaps that might be more true w/ a car that's been tracked, rather than just street driven.

jwmarc 01-28-2007 08:35 AM

The PDF shop manual has some info on the relays.. here are some photos....I will try and find some others and post.


http://forums.pelicanparts.com/uploa...1170005411.jpg

http://forums.pelicanparts.com/uploa...1170005599.jpg

jwmarc 01-28-2007 08:39 AM

Here is another ....http://forums.pelicanparts.com/uploa...1170005977.jpg

jwmarc 01-28-2007 08:41 AM

So you see above that there is the yellow delayed action and the round charge pressure... If you have an older turbo ...I dont beleive the yellow realy is used...

jwmarc 01-28-2007 08:50 AM

Here is some more about the cut-off...http://forums.pelicanparts.com/uploa...1170006580.gif

jwmarc 01-28-2007 08:52 AM

Sorry if the prior was to small.. here it is again. http://forums.pelicanparts.com/uploa...1170006745.gif


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