If any of you have been following you may know I have been battleing this issue for some time on an 84.

Tonight was the fist night I have really been able to dig into this issue.

Tonight I learned cylinders 5,6,7,8, are not running. I have checked everything I know of and this thing should be running.

The car has run like this since the day I bought it, I knew it didnt run.

When I got the car it needed a TB job. It was not broke but it was about too. this was completed.

When i got he car i found both cams to be off 2 teeth counter clockwise. fixed with TB change. (FYI)

Compression was tested on the engine twice, both times I got the same numbers of about 155# on all cylinders.

Then I thought maybe fuel restriction, I verified, I have fuel all the way through the rail

Then I thought maybe injectors... I pulled Cyl#5 injector, cranked the car with the injector in my hand, My hand got wet with gas and i could see a fine mist coming from the injector.

My neighbor was over and said "maybe a cam is broken". So we pull the plenum and had him crank the car while I held my hand over the air intakes of each cylinder.. all 8 pulling air just fine, none puffing anything back out. I feel this confirms the cam is OK??? Does it?

I checked for spark and spark it fine. I even pulled my new dist cap off my 79 and tried it, same issue.

So I'm out of ideas.. HELP

Thanks.

 

Well, sounds like since the issue is on one side of the engine, it must be something that in related to that side. Spark, fuel and compression seem to work, but maybe you still have a timing issue or even still have a messed up cam.

Remember that if you're cam is off by 2 strokes, it will look like it's in sync when you check the marks, but will be opening valves when is should be closing them and visa vera. So... you may have to re-do that timing belt job and spin that cam a turn. - Ruf

 

You said USA but does it have a euro dual distributor?

 

Its Keyed, how can it be off? I also placed my hands over cylinders 5 and 4 intake tubes. thus if you look a the fire order you will see part of the order is 5-4... When my helper cranked the car, I felt sucking on 5 than 4. So i dont think its a cam issue. But thank you. for the reply becasue I am at a loss here

 

nope

 

Okay, I got one for sale NIB if you need it

 

you cant get normal compression if the cams are off a tooth or so, and the cams are broken. sounds like something electrical for spark. cap cracked or broken?

the fuel is distributed evenly on all cylinders, there is no 1-4and 5-8 sides of the fuel, unless its all the injectors or the fuel rail. spark is the cap and rotor with wires.. if one side is running , the other has to as well.

this is an interesting puzzle.

mk

 

Distributer green wire?

 

Did you check for spark on all those cylinders that are not running? It sure sounds like an electrical issue. Do you think it could be in limp home mode? Have you got an extra computer that you could swap out?

 

Do you have limp home mode on an early 928? I did not think so?

How do you know that cylinders 5,6,7,8, are not running? It must be hard to confirm?

Marton

 

About the cam question
The cam turns once for every two turns of the crank. So you could have one cam correctly set versus the crank and the other cam is one turn off versus the crank. I am no engineer so I have no idea of the effect; it is a 4 stroke so I assume it would be firing on the exhaust stroke not the compression stroke?

Marton

 

Shark Attack,

At the moment ..... the first thing to verify is correct firing order on the distributor cap: everything can look perfect ... but if two or more wires are crossed, nothing works .... but the wires will still show spark!

Anyway, that's the first thing I'd check: then ....

Did you check the FI ground wires on the left bank? You may have 12v at the injector 5-8, but inadequate amperage to fire them correctly: I confess that I can't recall if the 16v injector harness is split left - right, or split 2 per bank like the 32v ... but may be worth checking.
Another trick is to get a $5 'noid' light - it plugs into each injector lead, and indicates correct firing by its flashes

 

fire order checked and re-checked

I checked the voltage at the injector, not under load though

I have not seen any ground for the left and right.. this was my first thougth also

 

Im going to put my scope on it tonight (if i can find it, I have not used it for years) anyone know what im looking for as far as voltage on the injectors and length of pulse?

 

You may have one of the cams 180 degrees off from the crank. Verify that you have the valve timing of both banks phased properly with the crank. As you turn the crank over slowly in the correct direction, you should see the proper cylinderintake valve close followed by the rotor starting to lineup with its dist. cap electrode to enable firing. I suspect that the one bank is firing after the exhaust stroke instead of the compression stroke.