backnblack

Once upon a time I throght I wanted a 928 so I traded my old suburban for a 86
928s a little beat up but I thouht I could bring it back to be a daly driver and it did run when I got it, well over the summer it sat for 3 mounths and I power washed the motor before stared it from sitting and now tada I have a electrical
problem .
ok , the fuel pump does not run without a jumper from the battery.
no signal to the fuel injectors.
I tried to jump the fuel pump relay, nothing.
I took the injector relay out and jumped it ( 30-87)and it started to ground out.
well , thats where I am with it now, I'm not sure what to do from here.
anybody have any ideas ?

Regards
Matt

Alan

Matt,

We'll need some more info on what you did & what happened

I assume from what you say that it cranks but does not start?

You said "I tried to jump the fuel pump relay, nothing"

Regardless of if it started - did the fuel pump run (have someone listen @ the tank...)

If the pump seemed to be working anyway OK - leave it for now.
If not just test the horn - if OK swap the horn relay with the fuel pump relay - check the pump...

"I took the injector relay out and jumped it (30-87) and it started to ground out"

I have no idea what you mean when you say "ground out" ?

Possiilities for no-start (at all) when cranking are primarily, no fuel or no or wrong spark

You've been focussed on fuel. You need to check for spark next. Given the context of where you were spraying the water this seem more likely - I'd dry all the HT lines and leave the hood open for a few hours - nice sunny weather may help (order some up...) (maybe use a big hair dryer!....)

Having sat for 3 months could perhaps have created fuel issues - but its not that long...
(e.g. sludge bunged up pump or filters). Usually this wouldn't get bad enough to stop the car
initially starting unless the pump is completely out)

Tell us more on other symptoms...

Alan

backnblack

Hello Alan, no the fuel pump will not work without the jumper to the battery and the motor does crank.
I'll try to post more info when I get into it more, do all the relays jumper the same? ( 30 to 87 )
Thank you for your interest
Matt

Rich9928p

Check the fuel pump fuse - is it burned out, is there corrosion? In your case if the fuel pump runs, that is OK.

At the relay points, check for battery voltage at postion 30, it must be there at all times (always hot). All the relays in question are 30 to 87 jumpered.

Label the relay (position and function) and remove them.

The three relays that need to be jumpered to start the engine are:

- LH
- EZK
- fuel pump (the fuel pump should run as soon as the jumper is in place, if you don't hear it, stop the test and fix the problem (wiring or fuel pump problem)

If the car starts when jumpers are in place, the next step is to test to see which relay is bad. Remove one jumper, plug in a relay, crank the engine. If it starts, replace the next jumper with a relay. If it doesn't start, that realy is most likely bad.

If it doesn't start with all three relays jumpered, you have a problem elsewhere. There must be RPM pulses from the inductive engine position (RPM) sender to the EZF module. The EZF provides engine speed information to the LH, the LH won't turn on unless there are RPM signals and the fuel pump will not turn on (by virture of the LH closing the ground path to the fuel pump relay) until it sees at least 25 RPM crank speed.

There are a lot of tests to perform to find specific item. I have these tests on a website that seems to disappear each time I post it, so send me a PM and I'll direct you to that source.

Check these things out and let us know how it goes.

backnblack

What I know and checked
The car turns over.
It will start if I spray fuel or starting fluid in the intake.
the fuel pump does not run unless I jumper it to the battery.
With the fuel pump running on a jumper the car will not start, I have pressure to the injectors but I have no signal, I tested the injectors with a noid light.
I found the horn relay and took that out and then tested the LH, EZF and fuel pump relays by putting them into the horn spot and hitting the horn they all worked.
I went through all the fuses and they were all good.
I'm just not sure what to do from here, any ideas are very welcome, thank you.

Rich9928p

I tested the injectors with a noid light I have pressure to the injectors but I have no signal Did you check the voltage on the fuel injectors when the relay positions were all jumpered? There should be 12V at the fuel injectors when the ignition is turned on or relays jumpered. The LH fuel injection controller provides the ground switch, so if there is no switching when the engine cranks the LH isn't working - or it isn't getting the engine rotation information from the EZK spark controller (check the circuit EZK pin 13 to LH pin 1).

Have you tested the fuel pressure and flow? Just because the pump runs there could be a restriction, clog, etc.

Staring with starter fluid indicates that you've got spark, but if you have major vacuum leak, the injection system can't provide sufficient mixture. Have you checked the vacuum when cranking? This also could also be the cause of your problems.

Kevin in Atlanta

Warning: DO NOT use starter fluid. That stuff will seriously damage the bores if overused.

backnblack

Thank you Rich for posting some more things to try, I won't be able to do anything until tomorrow.
How do I test for vacuum leaks?
Do you know if there is a way to get more info of my car from the vin number?
thank you
Matt

Rich9928p

How do you test for vacuum leaks?
a. Gain access to the throttle housing by removing the airbox and mass airflow sensor, hook up a vacuum meter to one of the ports on the throttle body on the vacuum side (see the photo below) and see if the engine pulls a vacuum when cranking (don't push on the gas pedal). If there is little or no vacuum, you could have a leak in the intake system (gaskets) or one of the lines in the system.

For other system leaks, use a mighty vac and pull the system down and monitor the rate of draw-down. You then go after each vacuum circuit and locate the problem.

b. VIN: the only information that you'll get is the model year, if it was a North American car and the manufacturing number. PCNA can provide more information about options and original color if you pay them for a certificate.

karl ruiter

Most (all?) fuel injected cars have logic to turn off the fuel pump if the motor is not running. On some cars this is run off the ignition, while on others it is run off air flow meter, and on others it is run off a seperate crank based trigger for the injection. In anycase I think the fuel pump logic pretty much always goes through the injection box. I am not familiar with the 86, but if the car will run with starter fluid then your ignition is ok, but it sounds like your injection is not running the injectors and not running the fuel pump. Others will know more about this specific system than I do, but I would start by looking at the signals that trigger the injection (a crank sensor?). A wild guess is that you have some corrosion in the connector there. If that is not it I would sit down and try to understand what the components and signals in this system are and how the work together. Older cars with fuel injection systems commonly have problems with connectors and wiring and if you can understand the signals you can sometimes track it down a little more easily.

backnblack

Ok this is where I'm at today.
I have tested the relays by putting them into the horn circut and each one ( LH,EZF,fuel pump )they all made the horn blow so I take it they are all good.I disconnected the battery and tried to jumper
( LHXXV 30-87 ) and when I tried to connect the battery it arced ( grounded ) so I disconnected it and tried the ( EZF XXI 30-87 ) and it did the same thing ( grounded ). I can jumper the fuel pump
( XX 30-87 ) and connect the battery without it grounding, all the tests where done with no key in.
So I think I have a hot wire grounding somewere. I just don't know were to start, it shouldn't be a worn wire because the car has been sitting since the last time it ran .The battery was disconnected when I power washed the motor, although I did try to start the car before it was dry so I could have shorted something that way I just don't know.

Any and all help welcome
Matt

Mrmerlin

Hey bro, disconnect the battery clean the posts and terminals, then leave it disconnected, go to the right of the engine compartment find the wire harness that is connected to the side of the frame it is just in front of the strut brace remove this and open up the connector write down all of the wires and there locations, you shold see a big wire and a bunch of smaller ones.
The big wire will have insulation cracking and you may find some of the smaller wires do as well, get some heat shrink and cover all of these wires. Get some dielectric grease and put it on the pins of the connector. Put this back together.
Go to the fuse panel and remove it from its mounts so you can tip it foward look at the top of the fuse panel and see if water has leaked from your wash job ( water will come in around the heater/blower motor housing and leak onto the fudse panel, if this is happening it is time reseal the blower box) Remove the fuses one at a time and grease them put it all back together and see if this helps

backnblack

dose anyone know if the alarm system on an 86 928 is connected to ingnition or feul systems ?

T_MaX

You will need to check all wires and sending units under the hood (where the problem started)! I did this on my 300SDL when I first bought it. Turned out that after a few years a few of the senders were no longer water tight

Yes! But unless there is something your not telliing us, your time would be better spent looking for a shorted wire or a bad sender under the hood.

Imo000

Check the Fuel Injection Relay. Remove it from the panel and jump the sockets. If this doesn’t work the problem is probably with the ECM. I had this problem with mine and a simple jumper with a toggle switch fixed it until I received a new one.

Be careful, although a lot of the relays look the same yet they are internally very different. The Fuel Injection Relay is one of them. The replacement relay has to be the same as the original. Same part number and all. A regular replacement relay will fit into the socket but it will not work. For some reason this relay was designed differently then a conventional one. It is crucial that you use a proper one, otherwise the replacement relay will not work either.

In the mean time, you can do the following to test the operation of the fuel injection relay:

1. Remove the relay form the board and then carefully remove the aluminium housing.
2. Re-install the relay into the board with the housing removed.
3. Take one hand and physically push the contact point of the relay together to make contact. At the same time with the other hand turn the ignition key and start the engine.

If the relay is faulty and by physically activating it will make the fuel injection system get the needed +12V, and the engine will start.

The symptoms you’ve described are the same as when my fuel injection relay failed.

I hope this helps!