Autobaunauto

1984 928 s. Has a new fuel pump. Fuel pump relay has been jumped and is working anyway. Starved for fuel injectors not working. Has new injectors. Car starts for a second and dies out quickly. fuel injectors are not pulsing. I have good fuel pressure. Checked the ground to the fuel injector harness - it is good. Checked MAF it is working. Cold injector firing that is how it is starting/firing. I check out the injector computer and swapped with a working unit out of another 84 it is fine. I m not sure if the temp sensor would make the injecotrs not fire or not? Really odd situation. I have checked all the common 928 issues. Please help!!!

Alan

So maybe the ECUs don't think the engine is spinning properly - check the rpm/speed sensor.

Alan

BTW - Don't post two threads on the same topics - creates confusion... just stick with the initial one.

sjfarbs

I wanted to check in on this one and see if there was any resolve, before I start a new thread..
I have a US 84 with the exact same issue and symptoms. Starts for a second roughly and dies within the next 3 seconds.

Some more history, in the last 30 days I noticed while driving, at times, when I took my foor off the throttle the idle would drop to about dead, if I "goosed" the throttle it would come back up and continue down the road. But now it is a complete no start , in the same manner as the original thread here.

FP relay jumped, pump runs (have not put a gauge on the rail yet to check exact pressure)
Temp II reads 6k at 40 degree external tempature
12v at the injectors connector.

Alan ...... can the RPM sensor be read with a multi-meter to evaluate? What should it read..

Any resolve to to point me the right direction is appreciated!

69gaugeman

The injectors should have 12v constantly, it uses a switched ground to fire the injectors. The start might just be the fuel injected with the cold start valve. If you unplug the cold start valve and it does nothing, it would mean that the fuel pressure is likely ok.

Best money spent would be getting a noid light. A small light that plugs into the fuel injector connector and flashes as the injector pulses. Save a lot of headache in determining if the computer is telling the injector to fire.

I bought a whole set for all injectors off ebay for something like 30$

sjfarbs

Good idea .... $39 at Harbor Freight , I may run out and grab the set.

sjfarbs

Will the noid light pulse with the key in the on position or does the starter have to be engaging?

jayc67

No, the injectors don't pulse without the engine spinning. I don't think you see 12v at the injectors with just the ignition on, but I can't remember for sure.

davek9

You should see 12v at the injectors w/ key on, like Rob said its a switched ground.
You did change out the ecu relays, yes?

sjfarbs

Relay has not been changed yet. I need to order one ..... contacting Roger now.

sjfarbs

I figured noid light first ? If I get pulse, relay is good, yes?

davek9

if the injectors are not opening, then the noid light will just light up and u already know that if u see 12v at one of the injector leads, right.
As far as the relay goes, the bad contacts can give mixed results, can u swap a known good same relay, like horn ?

sjfarbs

Is that the same relay? According to the 84' chart they are diff part #'s....Roger is going to send me a new relay.

davek9

Don't know 84 w/o looking and u can do that, right

sjfarbs

LOL, yes I can ............ and have ! They are not the same PN's!

waynestrutt

Change the green coaxial cable coming from the distributor to the connector near the hot post.