Rip It

A clogged exhaust cost me BIG, but if u have had the car for awhile u probably would have noticed a power loss first. Starter fluid doesn't compare to gas. It's a cheap fast check, a pressurized exhaust system takes about 10-15 secs and shut-down, a couple minutes of bleed down and u can repeat the cycle. good luck

Jim bailey - 928 International

Bill if you run a jumper wire from the jump start post to the + terminal #15 on the coil small wire it bypasses a number of items and the car. In fact the car may continue to run after you turn off the key switch until you remove that jumper BUT do not run that way too long it sends to much voltage to the coil.

Lorenfb

"I need to understand the L-Jet control a little better, as I wonder if the AFM is shorting and turning off the injectors through another"

Since your vehicle is an 84S, it uses a LH system with a MAF and not the old
L-Jet system with an AFM. Per the wiring diagram, the LH system does not use
a cold start valve.

The most likely problems are:

1. bad fuel pressure - check system pressure
2. bad MAF sensor - disconnect & restart (check for different running mode)
3. bad fuel pump relay - bypass it so pumps run all the time
4. disconnect water temp sensor which will enrich - use an injector test light
to check for increased injector pulse width (same test for MAF checking)
5. bypass power to the LH control unit at the Jetronic relay (XXV)
6. check for proper voltage (>10 volts) on one side of the injectors
and to the LH unit

Note: The LH control unit (25 pins) which your vehicle should have is very reliable
and rarely if ever fails, not like the later 35 pin LH units (high failure rate).

Key Point: Since you indicate that engine runs continuously with
a spray into the intake, focus the troubleshooting on the fuel supply.

Jim bailey - 928 International

Loren his car is a USA 84"S" which is not LH and has no hotwire mass air sensor which is why I could plug his brain directly into my 1980 car and confirm that the brain works . So yes he has a cold start injector and no crank timing mark sensor on the flywheel. The 1980-84 USA cars all use the USA emissions legal L-jetronic with the 928 606 121 02 "barn door" air flow sensor.

jheis

This may be too obvious, but have you checked the fuel filter?

I had a similar problem a few years ago that was cured by simply replacing the fuel filter. Good luck.

James

Jim bailey - 928 International

James was that on your 928 ? I only ask because in all the years and thousands of customers I do not recall a fuel filter as the cause of a 928 not running.

Lorenfb

Even though it's not an LH car, most of the check list remains:

1. bad fuel pressure - check system pressure
2. bad fuel pump relay - bypass it so pumps run all the time
3. disconnect water temp sensor (pin 13) which will enrich - use an injector test light
to check for increased injector pulse width (same test for MAF checking)
5. bypass power to the fuel ijection relay & check for power at pins 10, 29, 14 & 15.
6. check for grounds at 5, 16 & 17
7. check for proper voltage (>10 volts) on one side of the injectors
8. check for the common grounding problem, disconnected grounds at back of head
9. Use test light to check for spark triigger signal to pin 1 of L-jetronic.
10. Check for varying voltage from AFM to pin 7 as the flapper is moved to full open,
from about 2.0 volts to about 9.0 volts with a good battery.

Whether a LH or L-jetronic system, the troubleshooting process is basically the same.

Bill Ball

Loren:

Points noted! I am fairly convinced by the symptoms and Scott and Jim's analysis that it is running briefly on the cold start injector and we need to diagnose why the main injectors are not firing. I suspect we did not effectively jump the injection relay. Also, I noted some irregularities in fuel pump behavior when I jumped the fuel pump relay that point to problems with the central panel sockets (I had to hold the jumper in and wiggle it a bit until it stayed connected). We need to clean them up.

You have given us good test points for that and other possibilities. Want to make a trip out to Concord this Saturday at 2PM?

Anybody in the Bay Area that wants to help us out, I will provide directions to Robert's house for the Saturday afternoon tech session.

THANKS!

jheis

Jim:

Yes, it was on my '82, shortly after I bought it in '94.

Car would fire and immediately die.

Maybe it was just a coincidence - or dumb luck, but I stuck a new fuel filter in and it started and ran fine.

Never had another starting problem until about a month or two ago when the FP relay left me sitting.

James

Thaddeus

Replace the fuel filter. Start with simple, dumb, cheap needs-to-be-done-anyway stuff. I've had cars act just like that with filters nearly plugged.

Bill Ball

OK, I'll pick up a filter for Robert, even though the symptoms are not what I would expect.

abbzer0

Just my $.02 tip here.. When I replaced my fuel filter, the old nuts were on SOOO darn tight, that (while counter holding it) it began to strip my wrench, even a line wrench. I ended up taking a large pair of vice grips and putting them on the nut, I got more pressure on it that way and broke them loose.. Just be sure to counter hold it well. Just incase you hadn't done it yet. Also, you may want to look at the fuel line from the pump to the gas tank. When I felt mine it was *REALLY* "squishy", not like a rubber hose should feel. I ended up getting some replacement hose at NAPA for free since it was the end of the box. Good luck!

DANdeMAN

I know it's an old thread but I'm having a no start problem that resemble this one.
Wanted to know how this one came out!?

I have the same 84S .....

Bill Ball

Sorry, we did not resolve it and I lost track of the owner. I emailed him a few times to follow-up but never heard back. I thought it was a fairly clear that he was running only on the cold start injector, but we did not figure out why.

DANdeMAN

Thanks Bill, alot of good info in this thread, will see what I can do....

So far, the pump is weazing and I get some sparks as the engine try's to start.

This is where I'm at now.
Next on the list is check if pump is actualy sending trough the filter(3 years old) and try some starter fuel to confirm spark.

The Relay as been replaced and all fuses are good.

I was driving and it just stoped without any hesitation..... Does not start at all except for the random firing

Yes there is gas in the tank ...