Turbo won't start: Suggestions please - Suspect Fuel pump

lomotpk · 02-26-2004, 04:29 AM

The car has run fine for a year, then on Sunday I washed the underbody with a gardenhose to clean off sand, salt, etc from driving around Boston last week. Then on Tuesday it wouldn't start. The details....

- The car has full power to dash, windows, etc.
- It turns over strongly.
- I have not done a positive spark check, but the car has twin-pack crankfire ignition. The packs are bolted to the rear wall cabin interior and are making their usual sparking/crackling noises when I turn it over.

So, I suspect the fuel system.

- Have checked fuses and confirmed voltage
- Have swapped out the two front relays, but upon testing the orginals power-up and switch.
- Have unplugged and replugged in the overboost switch connection at the motor.

So, what's next?

- Was thinking of getting under the car and directly jumping the #1 fuel pump to see if it 'works', but I don't know how to. Photos' would be apprciated.

Regards,

The loneliest turbo....is a broken turbo.

No Whoosh, no fun.

Lomotpk

ruf-porsche · ruf-porsche's Garage

The year of your car would help.

lomotpk · 02-26-2004, 05:43 AM

Sorry.

It's a 1984 930, with a 86 engine and mods. The only one probably relevent would be the ignition: twin-plugged with a crankfire system.

dean · 02-26-2004, 05:53 AM

You have to check for spark and fuel. For spark pull a plug wire put a plug in and ground it and crank. Fuel- ign on, pull aircleaner, push down on the flapper and listen for the injectors squeeling.

lomotpk · 02-26-2004, 06:11 AM

Dean, To clarify.

I've got a K&N airflow thing draped over the top of the engine.
(previous owner)

Do I need to remove the entire black-plastic housing first? or does one remove the 'cone filter' element and then reach a hand in?

Thank you in advance.

john walker's workshop · 02-26-2004, 06:54 AM

you can just push down on the spring loaded adjuster with your finger. it's the thing that you stick the allen wrench in to adjust the CO. no need to pull the filter housing.

lomotpk · 02-26-2004, 07:11 AM

Now that's a useful tip. Thank you.

lomotpk · 02-26-2004, 04:01 PM

UPDATE: I turned the switch and pushed the Spring loaded adjuster.
The relay in the engine compartment switches, and I can hear a chamber opening, but unfortunately no distinctive "roar" of injectors.

So...what now?

If someone can provide some advice I am interested in jacking up the car and applying current directly to the forward fuel pump just have a direct indication of work or failure.

I thank you all in advance.

dyerkes · dyerkes's Garage

Is it safe to assume that you have gas in your gas tank? Unless you are 100% sure that you have plenty of gas, you might want to at least put 1-2 gal. in before continuing. Jumping the pump will at least tell you if your pump is bad. Another failure point is the sensor located on your fuel regulator housing. It is intended to kill your fuel pump in the event of your car flipping.

Good luck,
David
1986 911 Turbo

jryerson · 02-27-2004, 01:30 PM

On the 2 fuel pump relays in front bridge relay wires 30 and 87 on both, you should hear both pumps running and try to start

gsxrken · gsxrken's Garage

Pushing down the flapper won;t kick over the pumps unless you have the wire unplugged form the back of the fuel distributer housing. Do that first, if still nothing I would suspect the yellow square relay on the LH electrical tray near the fuel filter. Wiggle it, spread the contact legs etc, if still nothing you can jump that relay with a little wire between 2 of the sockets. Memory fails as to which legs to jump across...

lomotpk · 02-27-2004, 02:41 PM

JR,

I thought the red relays needed to be jumped between 30 and 87a?

Thoughts anyone?

GSXRKEN, I'll pull the wireand check and also I'll do a search on the yellow realy for the jump pins.

Regards

john walker's workshop · 03:00 PM

if everything works as it should, pushing down on the flapper WILL activate the pumps, and squirt the injectors, with the sensor plate plug connected. that's what it does when air lifts the sensor plate in normal life. with the plug off, the pumps run with the key on, and pushing the sensor plate down will squirt the injectors. is the wire still connected to the overboost switch, which is just below the breather hose from the turbo sump, where it attaches to the air filter housing. the switch may also have an open circuit. ground that wire temporarily to bypass the switch. the switch activates the yellow cutoff relay on the engine area fuse board, which in turn, kills off the function of the front FP relays.

jryerson · 02-27-2004, 03:59 PM

Some have red fuel pump relays, they are the last 2 relays in the fuse box closest to the firewall in the front trunk.

gsxrken · gsxrken's Garage

John Walker is right- when you disconnect the wire on the fuel head, the pumps should squirt when the key is turned on. Been awhile, thankfully, since I got intimate with the fuel circuit. That yellow relay is still a prime suspect, however. I've also heard tell of difficulties with a rev limiter in our 930s that can interrupt the fuel circuit. Perhaps a search would help.

Good luck and let us know what it turns out to be! Between me screwing you up further and John's dissing of our fine President in his signature... it just goes to show that no one is right all the time.
:-)

lomotpk · 02-28-2004, 06:17 AM

UPDATE: Good News, Mysterious News.....

This morning I was able to determine the following:

[1] Both fuel pumps work fine. I got under the car and applied direct current and they both work well.

[2] I was actually able to get the car to start and it ran for a while. Then I shut it down. went inside and tried to fire it up again. It won't start. Even after a lot of voodoo electrical fiddling (this plugged in, but that not...)

So here is the interesting/mysterious part...

-Sometimes when I jump sockets 30 to 87 on the Red Fuel Relays, the pumps run. Sometimes, not.

So, I think the key question is,

Under what condition will the fuel pumps not run, when the red relays have been bypassed? Specifically, when I'm applying nice hot current from socket 30 to socket 87, what is interupting the current so that the fuel pumps do not activate?

Once again, my thanks are in advance.

Richard/Lomotpk

lomotpk · 02-28-2004, 09:02 AM

Further Update:

Here is the current state: I've got the car running, but not optimally.

-Cleaned all contacts, fuses, relays, tightened battery connections.
-Charged the battery (it was a little low, but the starter motor still turned strongly)
-Pulled the wire on the fuel head, so that the pumps run all the time.

5axis · 02-28-2004, 09:41 AM

Under what condition will the fuel pumps not run, when the red relays have been bypassed? Specifically, when I'm applying nice hot current from socket 30 to socket 87, what is interupting the current so that the fuel pumps do not activate?

The factory alarm can get goofy and it shuts off power to the fuel pumps. I recall a thead explaining how to jumper/bypass the alarm.

lomotpk · 02-28-2004, 12:53 PM

Keeee-Rist!

Now it won't start. Now it will start. It's completely random.

It's Miller Time folks. We'll try again tomorrow.

jryerson · 02-28-2004, 07:19 PM

On some turbos their is a delayed ign/fuel pump relay cut off located in the back fuse/relay area next to the cd box.

Its shuts off the fuel pumps first then the CDI 3-5 secs later,its a small silver box relay on the very back closest to the rear of the car, their are 2 red hot wires going thru it, you may try and bridge them.

Also check the boost override switch next to the boost sender on the intake, its a white wire you supposedly can ground it to by pass it