Lonnie G.

First post so please bare with me. I have owned this car for a year now, didn't run when I bought it. So far I have replaced gas tank that was leaking. Fuel pump and filter that was missing, plugs, distributor cap, rotor, and wires. Temp sensor II, all vacuum lines, o-rings and boots associated with intake. Ran a compression test, all cyclinders 165 psi, + or - 5psi. Also replaced ignition module. Motor turns over fine, it has good spark and fuel pressure is 40 psi. It is not firing the fuel injectors. Took control unit and tried it in another car and it worked fine. I have bought the full set of manuals and have used the trouble shooting charts to no avail. I have a scope and can see the signal from the ignition to the fuel injection. Power and all signals look to be proper. But it still wont run. Let me rephrase that. It wont stay running. It will run for a second or two then stop. I will not give up on this project, I've always wanted a 928, now all I have to do is make it run. If anyone has any ideas it would be a great help. Thanks. Lonnie <img src="confused.gif" border="0">

Randy V

Welcome to the 928 Forum Lonnie.

Does this sound similar to your problem:

<a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=14&t=003282" target="_blank">http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=14&t=003282</a>

Rich9928p

Lonnie,

It sounds like you've done all the correct things. I find that with these problems you have to go back to square one and eliminate each possible problem systematically. Even double check the stuff you've already checked.

You need air, fuel, compression and spark all in the correct quantities for the engine to run.

I'm assuming that you have verified that you have spark and the timing is correct.

If it starts but doesn't stay running, that can be fuel and vacuum related problem. Have you verified that your system is holding a vacuum? My '83 A/T up and died one time and would run for just a while and then die. I thought for sure it was fuel related. It was a major vacuum leak. The A/T cars have big caps over vacuum ports on the passenger side of the throttle housing. If one of these caps leaks it won't run.

If you get no fuel from the injectors and verify fuel pressure, then somewhere between the battery and ECU or ECU to injectors is the problem. There is a separate wire from the battery to the ECU relay. Check to see that the wire is connected to the battery and you have continuity (yep, that was an intermittent problem that I had and it took 6 months of on and off trouble shooting to fix). Check the voltage at both sides of the AFC relay. Check the engine speed input to the ECU, I believe it comes from the spark module. Check the relay for the fuel pump.

There are a million other possibilities. You just have to track them down one by one.

Good luck, once fixed my ’83 runs GREAT.

Rich

Lonnie G.

Rich,
Thanks for the reply. Started over checking everything. Power from battery to ECU is correct. Speed signal from ignition module is there. Checked timing of crank, cams and distributor, also all correct. Cleaned all ground connections above fuse panel. Also am I correct that if fuel pump relay pulls in than I am getting a pulsed signal from ignition module? Also checked caps on throttle body ports. I just can't get the fuel injectors to fire. I don't know where to go from here. Thanks, Lonnie

WallyP

1) Go to plug W (red plug near right end on bottom of central power panel) and make certain that it is properly seated. If so, find the red/black wires coming out of terminal W2. With the ignition on, check for 12 vdc on the red/black wires. Check for 12 vdc on the red/green wires coming out of W3, red/blue wire from W4, and the red wire from W5. If the wires in these four terminals have 12 vdc, the ignition switch and fuel injection relay are working. If these wires do not have 12 vdc, there is a problem in the igniton switch, the fuel injection relay, or the wiring.

2) Hook an analog voltmeter (moving needle) to the black/green wire coming out of terminal W6. Check for pulses while the starter is operating. If there are no pulses, the connection thru the central power panel to the green wire going to terminal 16 on the ignition control box is bad, or the ignition control box is bad. Check for 12 vdc on the black/green wire from W7 while the starter is engaged.

The injectors get 12 vdc from terminal 87 on the fuel injection relay in four groups of two injectors. The ECU grounds these groups to fire the injectors on terminals 14 (green/red), 15 (green), 32 (gray/green)and 33 (gray/black) of the ECU.

If the ECU has power from W4 and W5, and a pulsed signal from W6, it should give a pulsed ground to the four groups of injectors.

Lonnie G.

Wally,
Thanks for the reply. W3,3,4,&5 all have 12VDC on them. W6 has pulses from the ignition module. W7 has power while the starter is engaged, but it still does not fire.
One question I do have, what resistence should I read across the injector. I've looked through the manual and can't find anything for the L system. I did find a spec for the LH and it says 15 ohms. The part # is different. Just wondering what I should read.
Thanks, Lonnie <img src="confused.gif" border="0">

Lonnie G.

I meant to say W2,3,4,&5.


Lonnie

WallyP

It would seem that if you have four groups of two injectors that no one injector can kill the entire system, so I doubt seriously that it could be a bad injector.

soontobered84

When you guys are talking about terminals being numbered:
(1)Are you speaking of the main fuse and relay block?
(2)How are they numbered? (besides the relay and fuse numbers)
(3)Are you speaking of the numbers on the back of the relays? (Our previous owner substituted generic relays for almost all the specific relays)
(4)Can you give me the location in the manual for the numbers you guys are talking about, so I can track down a perceived fuel pump problem that I believe to be present in our car. Thanks to all for this forum.

WallyP

When you guys are talking about terminals being numbered:
(1)Are you speaking of the main fuse and relay block?

We were discussing the plugs at the bottom of the central power panel that carry most of the circuits in the car.

(2)How are they numbered? (besides the relay and fuse numbers)

The plugs are lettered, starting with A on the left end, and increasing to the right. There is no plug lettered I (i), but there is an O (o). The 1980 - '83 (I think - perhaps '84) cars had two odd plugs in the middle. The vertical plugs were A thru X (skipping I), with Y and Z being the two horizontal plugs in the middle.

The later car's plugs are A thru W, with no Y and Z in the middle.

The wires are numbered in the plugs, but the easiest way to find the wire in the plug is by color.

(3)Are you speaking of the numbers on the back of the relays? (Our previous owner substituted generic relays for almost all the specific relays)

Not when we say something like "W4". The terminals on the relays and sockets follow a DIN standard, so that 30 is battery power, 15 is switched power, 85 and 86 operate the relay coils, 87 is the relay load, etc. These terminals are identified on the relay covers.

(4)Can you give me the location in the manual for the numbers you guys are talking about, so I can track down a perceived fuel pump problem that I
believe to be present in our car. Thanks to all for this forum.

There is a photo of the 1980 central power panel on page 90-21 in Volume V.

WallyP

Sorry - I forgot to mention the best source of info for the central power panel. I suppose that I keep thinking that everyone is familiar with our web site.

David has the fuse, relay and plug locations for all model years in the Tips & Links section of the 928 Specialists web site at

<a href="http://www.928gt.com" target="_blank">www.928gt.com</a>

rjtw

Hi Lonnie,
This is my first post to this board too. I too have an 83 928s, and mine too had the same problem: it would start fine, run for a second or two, and die. Good news: I've got it working now! In the end, it turned out to be a bad fuel injection relay (the one with the green dot on top).

The car was running fine when I ran it into the garage, the car sat about six months while I was off busy with other things in life, and when I tried to start it again... it wouldn't stay started. Hey, what's up with that?

I finally got serious about debuggging when I saw your post the other day. It really encouraged me to get out there and get it going again. Now that it's going, I became a member (so I could reply!) in the hope that this will help and encourage you too!

I narrowed in on the fuel injection relay from a process of elimination. I knew I had spark since the darn thing would light off and idle strongly (if only for a moment). The spark is either there or it isn't, it won't disappear after a moment of running.

However, I noticed that after repeated starting (say a half a dozen times), it wouldn't start. If I waited until the next day, then it would start right up and I could repeat the cycle.

I also noticed that the engine didn't die abruptly, but rather would choke to death... it would get slower, rougher, and finally stop.

One more clue: The engine wouldn't start at all if I depressed the accelerator more than the slightest amount while starting. Likewise, once it started, depressing the accellerator would kill the engine.

I formed a theory that the car was getting a puff of gas from the cold start injector and surviving off that until it was used up. That would explain why, after a few starts, the car would fail to start: it would generate enough heat to turn off the cold start injector. And thus I could repeat the cycle when it cooled down. And it would explain why pressing the throttle killed the engine -- too lean.

I also figured the vacuum system etc. was intact since the car idled well for a moment, but I did run through and check all the lines. I also checked all the infamous grounding connections.

A local shop suggested that the engine was probably getting flooded or getting starved, which fit in with my conclusion as well. To test the idea, I unplugged the cold start valve. I figured that the injectors were getting NO fuel at all... if they were getting any, the engine should still fire off (or come close to it) with the cold start valve. The engine didn't make a peep (of firing off).

At this point, I concluded that the injectors were definitely squirting no fuel. So it's either mega-expensive brain box time, the injectors were all stuck shut (highly unlikely), or no signal to the injectors... bingo, the relay, a cheap experiment. (My first inclination is almost always to suspect something electrical in these cars). $15 later, it fired off immediately. I'm very glad I was able to stop here, because the next guy on the hit list was the brain box.

Along the way, I chased down a bunch of alternatives too. At the risk of repeating other's advice, here's my own:

- Vacuum. Make sure all the lines are plugged in etc. From your first post sounds like you're in great shape here.

- Fuel. Can you hear the fuel pump running for a moment or two after the engine dies? I forget, did you perform the volume test? This might be a point to investigate since you changed out the gas tank...

- Signal at the injectors. Your first post said you had signal... did you verify this at the injectors themselves?

- Fuel at the injectors. The next step in my own debug process was going to be to pull out an injector rail, put plastic baggies or something over the injectors, and crank the engine just to see if anything came out. I'll just about bet you're not getting fuel there.

Backup test: Even of nothing comes out, it could be because they're just not opening. You could keep the rail in place but just loosen one of the injector rail connections, cover with something suitable and crank the engine just to make sure fuel squirts out. (OK, it's a poor man's pressure test; the right way would be to somehow measure pressure up there).

If you seem to be getting pressure in the rails, but nothing out of the injectors, I'd say signal or the injectors are stuck.

My local garage had another bit of sage advice on this one: Stick a bottle of Techroline in the tank, make sure you have fresh fuel while you're at it, and see if that doesn't help loosen things up.

This would also help the opposite problem, if you're getting flooded because of failure to close the injectors!

- Check to make sure the air flow sensor isn't sticking.

- Check to make sure the auxiliary air valve is partially open. This was one of the first things I checked. That could also, I believe, explain a start but failure to idle condition (if it's stuck shut).

- More electrical: Check all the grounding points you can find. The one I've had the most trouble with is the one underneath the metal plate that holds the hood latch at the front of the engine compartment... I think it's kind of underneath the small window-squirter bottle (it's been a while since I was underneath there). There's a grounding point up there that has three or four wires coming in with O-shaped connectors on them. Take them all off, revitalize with steel wool or fine sandpaper, and put back together.

Heck, while you're at it, the other standard advice is to check out or clean every connector under the hood that might possibly be involved with spark or fuel, and also while you're at it twist all the fuses round and back, and pull out and reconnect all the relays too. It's amazing how many problems come up in European cars (older ones, anyway) because of stuff like this.

The really GREAT news for you is that your brain box is working. As far as I'm concerned, that means that you won't have a big problem here -- it's probably something little, like mine was.

I hope this helps, Lonnie -- do the symptoms match what you're seeing too? The key point for me (and the most frustrating) was that it would run so well, but just for a moment!

Let us know how you make out. Good luck!
Rick

Lonnie G.

Rick,
Thanks for the reply. I have been fighting with this Bosch L-jetronic for over a year off and on. I have replaced every sensor except for the air flow meter on this car. I bought another control box because everything pointed to that, but the injectors still do not receive a signal to fire.
I am finally going to accept defeat. I am ready to replace the Bosch with something a little more up to date. Something that is programable and alot more user friendly.
Have already put out some feelers on different control units. It will not be cheap, but I'm sure it will run when I'm done. So if anyone is interested in a couple of Bosch L-jetronic controllers for a fair price let me know. Anyway thanks to everyone that offered assistence.

Lonnie

KBlair

Just wanted to let you guys know that I , also, am having a problem with my 1983 928S and that this thread has been most informative.

My symptoms go like this. Car sits for a week. Sat morning I go and start the car. She starts fine, and runs fine for approx 15 seconds, then chokes and dies. Restart, starts fine, then will choke and die. I kept doing this twice more until finally she smoothed herself out and ran properly. This has happened every week for the past month. If I give the gas pedal a slight tap while she's choking I can keep her from dieing and eventually she will smooth out. Once running, I have no problems at all for the rest of the weekend.

Considering I can get and keep her going, I'm going to start with the ground points and electrical things, then move to the fuel pressure measurements. I will have the injectors sent off the be cleaned and matched at some point as well.

rjtw

Hi Lonnie,
You are one BRAVE dude!

I hate to see you go to yet more expense when you seem so close. So, realizing how easy it is to be an armchair mechanic (and of course free advice is worth what you pay for it ;-) it seems to me you've got a grounding problem.

If I understand Wally's post correctly, the injectors receive 12v full time, and the EFI box just switches to ground at the appropriate times. So, a cheap & cheerful test would be to simply a) verify that you're getting 12v at the injector during starting and the few moments of run time, and then b) manually grounding out from the injector. I assume that grounding opens the injector (it could go the other way too). In either case, grounding should either make the injector squirt, or stop it from squirting. In fact if you have a spare injector lying around, just hook it up and you can probably hear or see it activate (though I'm just guessing).

All of which is a long way of saying this sounds like yet another incarnation of the bad ground problems. And the engine runs for a few moments from the cold start valve, like mine did. (Hmmm, come to think of it, a few years back I once had a no-fire condition when warm and had to have the car towed... it went away when I fiddled with ground points). Can you find out where the EFI grounds out the injector circuit and check that?

Sorry if I'm repeating the obvious, and it sounds like you're WAY ahead of me and you've probably already done this a long time ago.

Once again, good luck -- and thanks for giving me the impetus to get my own car going!

Rick