CIS Help - 930 cutting out when shifting -

ZCAT3 · 08-05-2004, 08:26 AM

Hi Guys, I have done my searches and read what I could find. I have bought the CIS pressure tester gauge (should be here soon) and am ordering a new check valve for the front pump and a new fuel filter. Before I get into checking the system I would appreciate any other suggestions of what to do while I am in there.

So here's the deal - the car is a modified 1986 930 with the Euro fuel system. The fuel head was recently rebuilt (September) and the car has run fine since then. Just last week my wife reported that the car died on her while she was on the freeway shifting from 3rd to 4th. She said after releasing the clutch in 4th and giving it gas nothing happened - the electrics were still working but it was as if her gas pedal had been disconnected. She downshifted to 3rd and after a brief hesitation the car came back to life and was fine.

Well the next day the same basic thing happened to me in a 2 - 3 shift. When pushing the gas did nothing I pushed the clutch in and the car completely died. While coasting I turned the key to off and then tried to restart it and it came to life no problem and was fine for the rest of the day (maybe 70 more miles).

The following day I drove the car to work as it is a short drive and I wanted to try to get a feel for the problem. No issues getting to work, but late in the day the car was difficult to start. At first it would just crank with nothing happening - even if I pushed the gas to the floor. So I stopped cranking, turned the car off and then turned it on without cranking. After a minute of sitting or so it fired right up. This scenario has repeated itself several times now.

Finally, yesterday it cut out on my wife again and she had to pull off the road as it would not restart. She coasted to the side, shut the car down, and then it fired right up again. Argh!!

So I will test both fuel pumps per the factory manual, and replace the front check valve if the front pump checks out bad. Any other suggestions of what to do or where to look?

Thanks.

beepbeep · 08-05-2004, 09:46 AM

I believe it's electrical.

Check both pumps altough I don't believe it's the pumps as it will run (altough lean) on one pump.

There is another culprit: overboost switch exists that will instantly cut power to both fuel pumps if boost rockets past 1.3 bar...if there is bad contact there, it will cut the pumps.

It is screwed into the intercooler. Check the wiring.

930 Guy · 08-05-2004, 09:53 AM

I agree it doesn't sound like a fuel pump problem. My car was cutting out on me, found the vac. advance on the distributor wasn't working all the time. Also check the line for splits. Could be a vacuum leak. To check it, pull the cap ( you might need to pull the intercooler) put a piece of hose on the vac unit (you suck) see if it moves. Your problem is a bit unusual. May be tough to track down. Brian

ZCAT3 · 08-05-2004, 10:36 AM

Thanks Guys - the car uses an electromotive twin plug system, so there is no distributor. I was just out driving it to do some more checking and it turns out the car will die anytime you shift when the boost is over say .4 bar. The weird thing is that it will hold boost in gear up to .9 bar (the max boost I can attain - I have an EBC) and then will die as soon as the clutch goes in. So I was just checking all the connections at the pumps and they look o.k. Both pumps are getting 13 volts and seem to be at least running (they are fairly noisy - you can hear the front pump from in the car). I will go check electrical connections in the engine bay now. Anyone have a picture of the overboost switch?

ZCAT3 · 08-05-2004, 10:51 AM

O.K. - is the overboost switch in this picutre? I presume it is the orange thing or the black thing to the right and behind it. Assuming it is one of these protuberances, then how can I check it. Each has a wire going into it that seems firmly plugged in.

E Ray · 08-05-2004, 11:04 AM

I had a very similar problem a few years ago, same symptoms, driving along than the car would die, usually during a 1st to 2nd shift. I also experienced intermittent hard starts when cold. Went thru the whole fuel pressure and ignition diagnostics and came up with everything being OK. Ended up changing out the fuel pump fuses and relays, still need to go back and clean the contacts, but it seemed to do the trick.

Eric

beepbeep · 08-05-2004, 11:04 AM

Nope. That looks like transducer for boost-gauge. you'll be looking for something that looks like oil-pressure idiot-light switch. It'll dig out the pic...hang on a sec.

beepbeep · 08-05-2004, 11:07 AM

Here you go, from my car:

...it's the thing right beneath the recirculating-valve cavity. It's not on the intercooler but the plenum. Sorry, my bad, i haven't been fiddling with 930 for a while...

baratta930 · 08-05-2004, 11:16 AM

I'll second the check the fuse comment. My car had the exact same problem, drove me nuts. Finally was changing another fuse and noticed that one of the fuel related fuses (can't remember which) wasn't looking too good. cleaned the contacts and replaced the fuses (checked the rest adn replaced any that looked suspect) and haven't had the problem since ...

hope this helps ...

ZCAT3 · 08-05-2004, 11:38 AM

Goran - thanks for the picture. I presume you are talking about the screw in sensor with the electircal connection attached to it that is pointing right towards the camera. Where is this in the car? From the shop manual it appears it should be on the driver's side of the engine bay near the back but I cannot find the damn thing.

I have check the fuse - it looks like new - the relays are new, I check all the connections at the pumps. The hose clamp for the line out of the gas tank to the front pump was not as tight as it culd be, so I tightened that up. The car seems to start right up now over and over in the garage, but that probably means nothing.

ZCAT3 · 12:38 PM

So I just took the car for a test drive - it cut out the first time I hit boost and shifted. Back in the garage to pull the IC and look for the overboost switch - which I still have not found. My mechanic thinks the overboost cutout may be disabled on my car as I have a Kokeln IC and an ApexI AVC-R boost controller?? In any case, I did find a wire that is just hanging loose - you can see where it attaches to the left side of that sensor. Doeds anyone know what this wire is?

john walker's workshop · 12:57 PM

looks like it's from the cold start thremo-switch on the face of the left chain cover. not too fun to reinstall on a 930.
unplug the sensor plate contact and see if that helps. bypass the delayed ignition cutoff relay by removing the plug from it and bridging the two wires in the plug that are closest to the engine. be sure the overboost switch is connected, and if there is none, the wire needs to be grounded. you can temporarily test the overboost switch by grounding the wire to bypass it. sometimes custom intercoolers are not grounded due to rubber mounting, so if the switch is on the I/C, an additional ground wire is needed. there is an overboost relay, generally yellow, on later cars, on the engine relay panel that gets tipped over a bit and looses it's connection with the plug, which shuts off the fuel pumps.

Slant930 · 08-05-2004, 12:53 PM

If you have a Kokeln intercooler, the overboost switch should be mounted on the intercooler itself. It is on the backside underneath. But looking at your first picture, your's seem plumbed different than mine. Beep is right, the orange thing is the transducer for the boost gauge. Mine has the overboost cutoff connected to the port where you have the black hose coming out of. I'm sure it's in there somewhere. The overboost switches can be flaky and cause cutout problems. Definitely sounds like an electrical issue.

Timothy

ZCAT3 · 08-05-2004, 01:27 PM

John - I was able to plug the wire connecter in to the other side of that sensor using some long nose pliers - I presume that is where it belongs? The other stuff you said was a bit over my head. I do have a Kokeln IC and the IC itself is grounded to the fan housing via a brown wire (see picture). Looking at the pictures of the underside of the IC is the overboost switch there?

Slant930 · 08-05-2004, 02:01 PM

I assume the black and gold thing to the right of the boost gauge transducer is the overboost cutoff. Seems to be something aftermarket as it looks different than what I've seen. Mine looks like in Beep's picture. It might be worth swapping it out for a new one, they are fairly cheap I believe.

Timothy

ZCAT3 · 02:39 PM

Well I assume that it came with the Kokeln IC but what do I know (obviously not enough) -

Where can I get a new overboost switch?

EDIT: So I pulled that black piece off and it is a pressure switch from Hobbs Corp as seen here: http://content.honeywell.com/sensing/hss/hobbsparts/products/pressureSwitches.asp

What is interesting is that the web site says these should not be used in areas where the temp could exceed 250 degrees -

beepbeep · 08-05-2004, 02:42 PM

You can ground the wire going to overboost switch for time being, it will disable the switch. But remember, switch is there to safeguard your engine in case wastegate fails or you will suffer runaway boost.

Switch on my picture is connected to flat intake plenum that sits after throttle.

ZCAT3 · 08-05-2004, 02:49 PM

Thanks Goran - so you are saying to unplug the switch and ground the end of the plug that was plugged into the switch?

I will try this and see if it works. Did you see that link to the Hobbs switch? My switch is a dual terminal switch with a part number of 76576. This is listed on that site as a 10 PSI switch??

beepbeep · 03:22 PM

I'll give you longish but possible explanation of what might be happening on your car, from engineers view:

Ze grand theory:

Your switch seems to be some sort of aftermarket switch, low rated (at 10 PSI) to boot. To make things worse, it isn't mounted at it's original location (after the throttle) but on intercooler.
When throttle is closed (during shifting, for example), turbo still spins trying to blow air into closed throttle. This will briefly pressurize the intercooler until BOV gets rid of pressure. Your BOV is smaller than OEM one so it will de-pressurize the intercooler slower than original one, creating bigger pressure peak in intercooler. All this doesn't matter if switch is located after throttle as it will only see vakuum after thottle is closed -> no boost peaks there. Unfortunately, somebody relocated it to intercooler in your case which I see as unwise decision for reasons stated above.

Your switch is made to cut near your real boost, so it's quite possible that it's been tripping on every full boost shift (and you wouldn't be noticing it). Those switches weren't made to continuosly cut 20A of current going to both fuel pumps, so continious tripping will make it's contacts arc and wear.

My guess is that your switch has been tripping for long time and finally wore down to point when it cannot provide solid ground in reasonable way, making problems.

I suggest grounding the wire for time being (and keeping an eye on boost gauge in case wastegate fail) and gettin decent 18 to 20 PSI switch, to be installed after the throttle where Ferry intended it to be.

Big intercoolers are nice but people tend to overlook small details that PAG put lot's of thinking into.

Now it can be something else but I will be damn proud if it's like I said

ZCAT3 · 04:17 PM

Goran - I would so like ot make you proud on this one. If you are correct it makes you wonder why Kokeln would have set it up this way. In any event, I went to ground the lead coming into the switch and it is a hot wire. When I put it against the fan strap it makes quite an electrical clicking noise in the engine bay and managed to shock me pretty good. So I just unplugged it and left both ends dangling for now. I did a brief test run and it did not stall the 2 times I hit good boost in second and then pushed the clutch in. I plan to go for a better test run shortly.

EDIT: Well that didn't work - just did another test drive and it cut out again. This is getting embarassing. How do I ground a wire that is hot??