jwillman

I finally tried to start the car today after a month of working on brakes and clutch system.

The car cranks nicely and starts immediately (despite not running since I brought it home 2 months ago) but runs for just a second or two and then quits.

I realize this could be a million things but I was wondering if there is a troubleshooting guide some place that outlines the things I should start checking and in what order?

I did some searches but was apparently being to specific as I cointinued to get no matches.

Thanks

Mrmerlin

it sounds like its running on the cold start valve so you have fueling issues

jwillman

So I should check fuel flow rate to the WUR first?

jpitman2

Pull the return line(where it crosses the cam cover), extend into a container, bridge pump relay - should get ~1300ml in 30 secs. If this not ok, change the filter (unless you know its been done recently), try again. Remove the air cleaner assembly completely so you can see the air plate, and with somebody else cranking it, see if the plate moves. Try pushing the plate - with pressure in the system, it should resist movement, but without pressure should move easily.
The cold start valve is electric, but the main injectors are mechanical, so I think you need to get a pressure guage on the system. This splices into the line from distributor head to the wur. With pump running, you should see ~20psi at ~68F, less at lower temp, a bit more at higher with the tap OPEN. If you have a high pressure here cold, it will not be rich enough to run cold. Your best trouble shooting guide is Ben Watson book on Bosch Injection....getting expensive lately - look for used ones on Amazon.
jp 83 Euro S AT 52k BTDT.

Dennis Wilson

The relay may be bad or it could be that the relay is not getting a run signal from the engine. Try bypassing the relay with the 15 and 87 connections. If it starts and runs the relay is bad or the contacts are corroded. If it doesn't run, clean the contacts at the ignition module and connections at the bottom of the fuse/relay panel. Also, all of your ground points should be checked/cleaned since the car has sat a while.

Dennis

jwillman

The wsm shows disconnecting the return line at the fuel distributor. Sounds like you are talking about the return line further down stream which looks easier to get to. Will both work?

PO claims he replaced filter but I am not confident.

So is there visual any way of determining whether I have a single fuel pump versus dual (in tank)?

Can / should I drain the fuel tank and if so can I disconnect the fuel supply line at the intake to the external pump and drain it from there?

jwillman

Is this different test than using pins 30 and 87 called out in the WSM to check flow?

Thanks

Dennis Wilson

Yes, using 15 and 30 only causes the pump to run when the ignition is on. Normally during cranking the pump is powered by the 50 circuit but once the engine starts and the key released, the relay looks for power on the 15 circuit. If no power on the 15 circuit, the engine shuts down. When you bypass the relay by jumping the 15 and 87 connections you are checking for an ignition signal. BTW the 928 is one of the few cars with a large enough 15 circuit (12 gauge wire) to power the fuel pump.

Dennis

chewy8000

Check the two fuel injector grounds... had me hunting for months. they bolt onto the passenger side fuel injector hold down brackets.

My car did the same thing start up for 2 seconds and die.

jwillman

So when I jumper relay 17 across pins 30 and 87 the pump immediately spins up and after a second or two begins to cycle and surge.

Normal or a problem? I don't know how much fuel is in the tank. Is it possible it is sucking air causing the cycling?

jpitman2

Cycling, surging pump? Cant quite visualize what would do that. It could be low fuel. Only thing that comes to mind is a blockage in the inlet line , but I cant see that stalling the pump. Is the pump noisy? Can you measure the current readily? I would do this at the relay socket, rto ensure there are no sparks up the back. Last time I checked mine it pulled 7A.
Can you open the access hole above the tank (in the hatch floor to the right side); there is a return hose into the gauge fitting - loosen the clip , and wriggle the hose off the fitting; connect some other hose to this hose, and run out to a safe container outside the car; jump the relay,and see if you get a steady fuel flow out this hose - which you should see normally. Also checking at the engine bay return line will tell you something useful. I suspect the use of the return line at the cam cover is because its somuch easier than at the distributor head. If you pull the gauge head out (disconnect hose and wiring pluig,undo the big plastci nut with 2 crossed screwdrivers), you will be ableto see into tank with a torch pretty well.

I have seen others with car sthat have sat for a while (esp CIS)get some gas in the tank, load it with more than usual rate of Berryman's, jumper the pump relay, and let it run for a while to circulate gas and try to dissolve any dried crud out and deliver it to the filter....
jp 83 Euro S AT 52k

jwillman

Pump is not noisy. It spins up and then quickly transitions to a cyclical churning noise like it is pulling a vacuum.

So if I disconnect the supply line into the pump should I get a free flow of fuel out of the in-tank pump? I did visually confirm I have an in-tank pump as the fitting has wires connected to two leads.

jpitman2

Can you see if inlet hose is collapsing, sucking in as the pump cycles? For testing purposes, any fuel resistant hose will do for that supply line. Once the tank is empty you could pus a rod through the old hose also. Or run a hose from the pump inlet into a can of gas, and see what happens?

Careful, Careful!!!!
jp

Landseer

It should run continuously and with a constant sound. Fuel circulates back to the tank.

Curious, same noise with gas cap loosened?

May be some debris in the pump. With some care, it can be reversed and cleared.

I've done it in-situ a few times, worried about a flash fire though. Best removed for this, and tank cleaned and strainer & hoses replaced.

jwillman

So I pulled the jumper and checked for voltage at pins 30 and 87 and have battery voltage, 12.8v.

I connected some aligator clips to the pump connections and I only read 7.5 to 7.7 volts with pump connected.