No injector pulse

stick1975 · 12-19-2008, 11:38 AM

I worked at a shop about 8 years ago and this 84 US 928 came in with a blown head gaskets and bad rad. tank. Well I got to R&R the heads (Dover Cyl. in Atl. did the machine work), the timing belt, water pump, rollers and seals. The car sat. for almost a year waiting on the owner. I ended up buying the car. It had no injector signal then. So I just put it in storage. I thought it had a bad ECM. About a month ago I pulled it out, drained the fuel tank and cleaned the cob webs out. I sent ECM and the Ing Modula to the ECU doctors in FL. Told them my problems, they sent my ECM and my Ing mod back. So I R&R my fuel pump, cleaned the grounds above the fuse box, and cleaned the connections I found under the hood. I hooked up the ECU and my Ing Modula and found that it would not spin with the key. So I jumped the 30 and 87 terminals where the starter relay goes with a starter switch just to see if it would run. With some fresh plugs a little transmission fluid in the cyl. and some fuel it did. So I mounted the ECU and Ing mod and now I have no Injector pulse at the Injector plug with a noid light. I have wiring diagrams, but it looks to me like both wires go back to the ECU on the diagrams, but on the car it looks like a least one wire is in the last plug on the pass. side under the fuse box. I think I have a bad connection some where.

Danglerb · 12-19-2008, 07:50 PM

Bad green wire from distributor to one of the boxes that never ever goes bad.

Landseer · 12-20-2008, 04:26 AM

Danglerb is referencing one achilles-heal problem, the green wire, a piece of coax with expensive brittle connectors that links the distrib to the spark box on the right fender, and noting that the Bosch L-Jetronic brains on the 83/84 models are rarely a problem.

What wiring diagrams are you utilizing.

Have you jumpered the appropriate relays on the CE panel at the passenger footwell?
There is a fuel injection relay that requires a three-wire jumper.

Grounds on these cars are a problem, so you need to find and clean all, if you haven't already.

The injector harness ground is hard to get at, located on the right side of engine, kind of under the cam cover.

My problem has been with relays. Do you have the CE Panel / Relay diagram?

Ignition switches are also a known weakness, you should replace, fairly easy, but pod needs to be dissasembled.

It is also possible for alarm problems to disable the car.

stick1975 · 12-20-2008, 04:29 AM

Green wire, are you talking about the that goes to pin 16 on the elect. ing unit. The other end is hooked to ter. 7? What should my injectors measure? I hope that it did not fry my computer. I looked at my diagrams again, looks like red+green and red+black go to ter. 87 on my AFC fuel inj. relay. Then it looks like the green, gray+black, gray+red go back to control unit. I have a red wire and red+blue wire that come from the computer and go to my AFC relay, but they hook to term. 87A. My AFC relay has no term. 87A. I know I have to be missing something simple.

Landseer · 12-20-2008, 04:38 AM

I haven't been versed in terminal by terminal work on the ignition unit.

The green wire we speak of is literally a green wire that you see in the engine compartment running from the back of the distributor, across top of engine, and to spark box near the jump terminal on the passenger fender. Sometimes it gets messed-up, esp. the connectors.

Do you have the Bosch fuel injection manual or the car electrical diagrams or both?

Have you jumpered the fuel injection relay?

Landseer · 04:50 AM

Try the link below, especially post 11, where Jack Riffle describes how to jump the AFC relay.

http://forums.rennlist.com/rennforums/928-forum/276663-no-start-whirr-whirr-no-catch.html

Also, Rennlist has deep archives that are easy to search and that will help you with this type of problem.

Also, I have an 84 USA 5 speed that I am driving sans interior, with all the electrical stuff exposed. Kind of a rolling labratory. If you need me to check or photograph something I can do it, or speak with you on the phone.

I also have an excel sheet I'm working on that maps what each wire on each electrical plug is connected to, it could help you also, but its not guaranteed accurate.

stick1975 · 12-20-2008, 05:15 AM

I have two different sets of diagrams. One looks like a "bed sheet" diagram from Mitchell on Demand, its about 5 pages that I have stapled together. The other diagrams I have came on DVD from the ECU Doctor in Fl. On both of my diagrams it says "note, wire color my not be accurate" and just a few say "NCA" color not available. I cleaned the grounds above the fuse and relay box, I have not cleaned the ground on the head yet. I will check that link too. I really appreciate any help I can get on this. When I first the car around 2001 or 2002, I could find a rebuilt computer for it, and that is why it set so long.

stick1975 · 12-20-2008, 05:31 AM

I have check for spark, and I do have spark. My fuel pump runs without jumping the relay. When I tried to start it after mounting the computer and spark box, witch are both rebuilt, it tried to start, running of the cold start injector I think. I tried again, and it would not run. I had spark, so I put my Matco Noid light set in the injector plug and spun the motor. No light. I used a long screw driver in the mass air meter to open the door about half way, to see if that would change anything and make my Noid light blink. Still no light. Whats so frustrating is that the ran when I first plugged the spark box and computer in.

Landseer · 10:26 AM

OK. The workshop manuals on CD, along with a lot of technical publications is available It has wiring diagrams that cover the whole series of years, specific to the year. ROG100 sells them --- contact him via PM if you want a copy--- great parts resource too.

Why do you think the problem is with the brain unit? Or wiring of it? Not commonly a problem on this model year.

Landseer · 12-20-2008, 05:33 AM

Did you put a three-way jumper on the fuel injector relay and try starting it?

Landseer · 05:51 AM

Here you can find a relay and fuse chart for the 83/84:

https://www.928gt.com/default1.htm

Am having trouble attaching excel sheet, so PM me an email address if you want and I can send that way.

The rennlist link I posted is just one of dozens on no start problems. Search there, it will help.

stick1975 · 12-20-2008, 06:12 AM

Looked at both links you listed. They spoke of my AFC relay, about how the 87A terminal is not listed, but that it is there. When I get home today I'm going to try jumping the #30 ter. to the #87 and #87A ter. where the AFC relay goes. I'm no expert by no means, but I thought it was the computer because I have fuel pressure, I have spark and I have compression. Most things I have worked on had the positive side of the injectors on a fuse, and the computer controlled the ground. The diagrams I have are kind of hard for me to understand the powers and grounds. I try not to just replace parts, I know allot of times if something won't run people say "it's the computer". I really do appreciate your replys Landseer, Danglerb.

Landseer · 10:28 AM

Try that. Also, if you have capability, take some digital photos of your CE panel for us.

Another quirk. You need to disassemble and carefully clean the contacts in the 14 pin connector that is near the jump post on the passenger side fender. I'd do this after you try the relay trick, its part of the standard revive maintenance. Also, consider at some point soon removing and cleaning your CE panel and replacing all those fuses (hard to see when they fail, gently run a finger up/down each to check. You may have a blown fuse that relates to your current issue and can't see the fact that its blown. (happens to me at least)

The CD's are about $80 or so. Best is to call and have a conversation with Rog100 who will help you. Or, Jim at 928 International, both post on this board, as well as own and drive 928s.
Check your PM's also and try to get me an email address. My excel spreadsheet will help you.

good luck with it.

stick1975 · 12-20-2008, 07:25 AM

My E-mail is stick1975@yahoo.com I think I'm going to buy some parts from 928Int. Looks like they got a good sale on used parts. I'll take so photos of my CE (fuse box/relay panel, right?) and post them.

Xlot · 12-20-2008, 12:45 PM

Quote:

Originally Posted by stick1975

Looks like they got a good sale on used parts. I'll take so photos of my CE (fuse box/relay panel, right?) and post them.

Here's a link to the wire diagram..

http://www.cannell.co.uk/928_Workshop_Manuals/1984%20Wire%20Diagram.pdf

Landseer · 01:25 PM

Nice, Hilton!

FYI, the 83 diagrams, if available, have a different layout format andshow wire colors, and are almost identical to 84 in function. Good to cross reference it against 84.

stick1975 · 12-22-2008, 06:37 AM

Thanks for the wiring diagrams Xlot. Thanks for everything guy's. I'm still new to this whole Internet thing, but I'm glad to have met good people like you all that will share information. Okay, I didn't get the time to do all the checks I wanted to do. Had to do the Xmas. shopping with the girlfriend. Jumped the AFC relay, tea 30 to 87 and 87A. Car still will not run. Tried on other check. I unplugged all the injectors while I had the AFC relay jumped. I then took a volt meter that was grounded to the head and checked for voltage on the red+green wire. It showed about 10.5 volts. So I had at least 1 volt drop. I checked it with a test light, and it would not even light up, and with my meter hooked to it at the same time, it now showed no voltage. I then took my volt meter and checked voltage at my AFC relay again. It had batt. voltage. So my theory is that I have a bad connection from my AFC relay to my injector. If the green wire that runs from Ing. control unit to my distributor was bad, it would not fire the coil, would it?

Danglerb · 12-22-2008, 11:51 AM

Green wire detects firing, not causes it.

Its a safety thing, without spark it isn't safe to squirt fuel into the intake.

All the injector wires are in parallel, so one short or partial short in the wiring takes them all out, but I'm not sure a voltage without enough current to light a test light means much.

stick1975 · 12-22-2008, 12:25 PM

Going by my "bed sheet" diagrams it looks like one side of the red+green and a red+black wire goes to some of the injectors, then the other side looks like it goes to terminal 87 of the AFC relay. If it does go all the way back to that terminal, than with the 30 and 87 terminal jumped, I think it should have batt. voltage. The other wire to that same injector looks like it goes to the computer, along with two or three more related to the injectors. I'm no expert by no means, and the wiring diagrams I have are hard for me to read, so if anybody sees I'm wrong, which I could be, have been before, and probable will be again, let me know, please. None of my Ford or Chevy buddies want any part of this car unless I "just put a small block in it".

Landseer · 12-22-2008, 02:07 PM

I'm a Chevy guy, too. Great for boats and trucks.

This engine is bulletproof compared to small blocks. And higher-revving. Its over 600 lbs of aluminum. Don't succumb to their thinking.

You need a three-way jumper wire to bypass the AFC relay. That was my issue with no pulse last year. Tore-up everything else before that, though, just like you are fixin to do.