Bill Ball

I went over to visit Robert Warner and see if we could figure out why his 84 would not start. Here are the diagnostic findings. Sorry for the long list, but probably the first 3 or 4 items will provide the right clue. The rest are just there to show you what we did.

1. Car starts, runs for a few seconds, dies. Car will restart once, die in a few seconds again. After that the car will not restart unless you let it sit for 10-20 minutes. Then behavior repeats.

2. The car will start and run as long as you shoot starter fluid into the intake.

3. Jumpered the fuel pump relay 30-87 - pump runs and fuel can be felt circulating in the fuel delivery lines up front. No change.

4. Jumpered the fuel injection relay 30-87. No change in the above. [Ooops! Didn't check to see if there were TWO 87 terminals.]

5. The injection brain has been tested OK by swapping into another car (thanks Jim).

6. Throttle position has no effect on starting. Holding throttle floored does not help it to start and run.

7. I measured resistance on the AFM contacts, but we are not sure of the correct values as they changed at some point during the production run. The resistance values were OK for a late version. Could a bad AFM account for this behavior?

8. I checked over vacuum lines and found nothing obviously wrong.

9. I pulled the vacuum lines from the fuel pressure regulators and the fuel dampener - no fuel in the vacuum lines.

10. The idle position switch was not being tripped, but I held that closed - no change.

So, we have spark. We have the fuel pump pumping. We get some gas delivery as the car does start. Once it dies, it will run on starter fluid.

All this leads me to believe that the fuel injectors are cutting out after a few seconds even though we jumped the fuel injection relay. What could cause that? Why does it not start at all on the third try but starts if you let it sit a while?

I thought perhaps the cold start valve was leaking and was flooding the engine, but when the engine ran fine on starter fluid, that points to a lack of fuel, not too much.

Fabio421

Be very carefull with that starting fluid or you may end up with bigger problems than what you started with. I'm not preaching, just trying to save you some $$$. Good luck.

AO

I was going to say it sound like a lack of fuel. I would veryfy fuel delivery volume at the fuel rail. If that's good, then it has to be the injectors, but I too don't see how this could be affected by the wait time. Hmmmm. It's got to be either fuel volume or fuel pressure.

macreel

Bill B... Fuel Pressure & volume at rails = ??

Is the MAF vane moving freely ?

G'luck.

Bill Ball

Yes, I think it's fuel. There are two fuel pressure regulators and one dampner and a check valve. I would ecpect the car to run unless both fuel pressure regulators failed. I guess the simplest thing would be to put a pressure gauge on the rail. The symptoms sure sound like something intervening and cutting off the injectors.

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 circuit not involving the injection relay.

The car had some weird aftermarket alarm that has been pulled out. I suppose we should bypass the factory alarm, but the symptoms are not what I would expect from an alarm gone bad.

Appreciate the warning about the starter fuid. We actually were using carb cleaner but didn't run it very long - just long enough to get a ways beyond the few seconds it would run unassisted.

PorKen

Temp II sensor bad, disconnected, or corroded (Temp II is on top of coolant crossover, with fuel injector connector)?

Is green wire green, or old and cracked?

Scott M.

Bill;

Sounds like the car is starting via the cold start valve (1st 7 seconds or until it warms up).

AFM is rpm based, meaning no fuel will be delivered unless the engine is spinning. Possible things to look at are:
-bad fuse (see Tareks post of 2 weeks ago)
-bad Temp II
-bad ign switch
-crank position sensor
-bad injector ground

Jim bailey - 928 International

Bill it is starting on the ninth injector the cold start . The injection brain needs to KNOW that the engine is running before it fires the injectors and continues to energize the fuel pump. The Hall signal generator in the distributor sends a signal via the infamous Green wire to near the spark box TSZ near the jump start post. The same signal also drives the Tachometer As I recall. So the injectors are not firing even though we KNOW the brain is functioning correctly and the temp 2 sensor is new. Also worth noting that when you jumper wire the fuel pump relay 928 615 119 00 it needs a Y wire to power up BOTH 87 terminals for the car to run.

rjtw

Been there done that. Infamous fuel injection relay (or equally infamous green wire, and associated Hall signal generator, as Jim beautifully sums up above) -- my money's on the relay. Sounds like you are already on your way.
PS could also be a bad ground from the brain, as the injectors get full time 12V and are grounded in banks of 4 by the brain to open the injectors.
Rick

Bill Ball

Thanks for all the excellent replies. As Scott and Jim suggest, it appears it is starting on the cold start injector only.

- fuses good.

- crank position sensor - if bad, car should never start, as you get no spark, right? That's the way LH works. Is it different on L-Jet?

- As Jim indicated, temp sensor II is new. However, the water temp sensor behind it looked pretty nasty (corroded connectors) - that's not a factor, right? Should clean it up anyway.

- I did NOT jump both 87 slots on the relay. Didn't notice them. Will do that.

- Green wire looks good. We have spark, so could it still be bad?

- Hall sensor. On later cars, if that fails, you just end up with retarded timing. But I gather it has more impact on L-Jet, from Jim's comment. Need to evaluate that item?

- ign switch - that occurred to me. We still have spark and if I jump the fuel pump and injection relays, it should bypass that issue, right?

- injector ground(s). Will check.

Thanks again.

Rich9928p

rank position sensor - if bad, car should never start, as you get no spark, right? That's the way LH works. Is it different on L-Jet?

> L-Jets don't have a crank position sensor. The engine RPM signal comes from the Hall signal, then goes to the transistor spark box, then goes to the L-Jet. Perhaps the transisort box output to the L-Jet is bad - or there is a break in the wire.

- Green wire looks good. We have spark, so could it still be bad?

> Sounds like the Hall sensor, green wire (shielded cable) and transistor box are working.

- Hall sensor. On later cars, if that fails, you just end up with retarded timing. But I gather it has more impact on L-Jet, from Jim's comment. Need to evaluate that item?

> It is a different system, there is no spark controller (just a switch), the Hall sensor runs off the distributor shaft. If you have spark, the Hall sensor is working.

- ign switch - that occurred to me. We still have spark and if I jump the fuel pump and injection relays, it should bypass that issue, right?

Correct

- injector ground(s). Will check.

The current path is 87 from the AFC relay to the fuel injectors to the L-Jet then to ground. So you need to check the wiring for the whole system.

Don't overlook a large vacuum leak.

Bill Ball

Thanks for the continued input! I did not jump the relay correctly (missed an 87), so that's first on the list.

Hey, Rich, very good stuff! However, I saw something that sure looked like a crank position sensor mounted on the top of the bellhousing. PET does not show it except for 85 on, so, you must be right. Wonder what that thing is?

Anyway, Robert and I will follow-up on all this good advice this weekend. Thanks again!

Rich9928p

Bill, you're referring to the test sensor. If you look, it isn't connected to anything! I guess back in those days they needed a TDC reference or something like that for their diagnostic tools.

Rip It

U will probably think I am nuts....sounds like a clogged exhaust system. Engine symptoms are as if it can't breathe, have someone hold their hand at the exhaust outlet on the initial 10 sec start up and feel if there is any air flow.

Bill Ball

Rip, you probably are nuts , but we will check it. There's just too much else pointing to lack of fuel. Runs great on starter fluid!