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740 what besides the ecu could cause injectors to not fire?

boostdemon

boostdemon

creative mastermind
Joined
May 31, 2002
Location
Cary, NC
1986 745 b230f LH2.2 (544 ecu)
Car sat for 10 years outside. Put gas and a battery in it and it fired right up and drove. Parked it in the garage and chassis fuel pump stopped running. Replaced fuel pump and still wont start. It has to be some kinda ground i'm missing or something that would deteriorate after running for the first time in forever.

- Pump runs
- Fuel pressure at banjo fitting for filter in front of check valve
- Spark plug dry
- Swapped out ECU to test

What am I missing?
 
Dan said:
this car have the injector resister pack, and radio suppression relay? those are issues
Click to expand...

Doesnt look like i have either where they normally are on drivers side fender:
sGaOvBRl.jpg
 
Yup, will check pump in a bit here cause thats easy. ECU... not sure what i should be testing there.

Crank signal... wire that goes up to the distributor on the back of the head? Something like that would make a lot more sense since the car moved and drove around and something 'broke'.
 
If it stood for 10 years I would replace or clean all fuses (might have corroded) and their sockets in fusebox. It caused me a lot of issues including problems with lights, cranking, etc.
 
Please tell us that you flushed the tank and verified that there was not rust present.

My car sat for 19 years and rust destroyed:
tank
lift pump
pressure pump
fuel distributor
control pressure regulator
cold start injector
injectors

PB101370.jpg
 
wujek said:
If it stood for 10 years I would replace or clean all fuses (might have corroded) and their sockets in fusebox. It caused me a lot of issues including problems with lights, cranking, etc.
Click to expand...

I pulled all the fuses, look good to me. I pulled the fuel relay and its clean no burns. I hear it (i think its the fpr) click on when i hit the ignition.

ZVOLV said:
Test lamp> power to injectors? Power to coil?

Spark?


Run on brake cleaner? Click my sig
Click to expand...
I have not tested signal on the injector plug... i was thinking a voltmeter but maybe a test light would be better, thanks for the idea. I did grab a timing light and checked that it was flashing to the spark plug signal.

I havent tested alternate fuels

TestPoint said:
Please tell us that you flushed the tank and verified that there was not rust present.

My car sat for 19 years and rust destroyed:
tank
lift pump
pressure pump
fuel distributor
control pressure regulator
cold start injector
injectors

PB101370.jpg
Click to expand...

Didnt flush it. Its plastic though right? I did think maybe i had a clog somewhere but i would have to pull the fuel rail off and test... and then i'd have to replace all the orings probably.
The car fired up and ran about 10 times over the course of a month for probably an hour total running time. I'd definitely consider that the intank transfer pump is dead, probably pretty gummed up as well... but i'm getting good fuel pressure in front of the chassis pump so i should at least be able to get something spraying at the injectors but doesnt appear to be. If the FPR was seized up it would still run right? just not under load when it needs to create more pressure in the line to keep up with consumption?
 
$5 noid light from IPD works great. $20 noid light kit is sold at auto stores. It takes 30 seconds to pull one out of the drawer and plug it in and then crank.

You can also put a screwdriver handle to your ear and the tip to the injector and crank it.

I ran outta gas recently and didn't wanna kill the battery cranking so I bought starting fluid at the gas station I limped into and fired the engine several times via spray down a disconnected PCV hose (1990 240). Ideally you want to open the throttle plate and get it into the intake. So... l eventually kept the engine running long enough it primed the system and I was on my way again.

I recommend brake cleaner/starting fluid to see if it starts. You can keep it running if you keep pulsing it into the intake. It's how we drive trucks with dead fuel pumps into the bay that we don't wanna push. One man is can-man under the hood pulsing spray into throttle, the other man is wheel-man and does the driving.
 
Last edited:
I just repaired a Bertone recently. The owner had been working on it for a year trying to get it running. It would start then immediately stall. Brand new plugs were fouled with nasty varnish. Injectors were bad. They were spraying liquid gas in there not atomized fuel. The Bertone sat four years.

I think the alcohol in the gas contributes to a lot of crud coming down the lines when you get a car running again after sitting.

But first make sure you have spark. If you do then the fuel system energizes. I would check the injector spray patterns if you aren't sure.
 
Little update:

- sprayed some starter fluid in the throttle body and it fired right up and ran for a few seconds (good ECU then right?)
- pulled fuel relay and confirmed its working
- swapped in good fuse to #1 (fuel pump, ECU)

Will test the voltage to the pump again in a bit... hopefully its not running because of voltage and not another ruined pump.
 
Runs on ether means the fuel system is NOT working. The ECU is part of the "fuel system". The ECU may be bad. Prob not.

Runs on ether= mechanicals and spark are ok. Time to shake down the fuel system....

Next is to check for fuel injector and fuel pump operation. First confirm voltage to the injector with a test light, or skip it and go right to a test light. Noid light is best here. Test lamp to injector negative, to ground. Crank. I think it should blink.

You could also just go one end of test light to a positive source, then other end to a (unplugged ) injector negative, crank. Blink=ECU is working.
 
On LH2.2, I think the spark circuits are completely separate from ECU and injectors. Running on starting fluid, and timing light working, implies good distributor pickup, EZK, ignitor, spark power.

Pumps not running would be the ECU and main relay. The injector power also goes through a couple connectors from main relay (the ECU grounds one side of injectors to turn them on).
 
Noid light. 30 seconds. No brain required to confirm power to injectors AND pulse. Every Turtlebricker needs one!
 
i have 2 ECU's, the one connected now confirmed working when i borrowed it the other day.

Fuel pump not running was how this ordeal began, put in a new used aftermarket pump and pump ran (relay working) and building pressure but wouldnt start. Now pump doesnt run on ignition again.

I will check pump voltage, and then also an injector plug for voltage movement on cracking.
 
Test lamp!!! Dont use a meter. One strand of wire can pass 12v and show as that on a meter, but won't run a pump.

You are close. It's either a dead pump/s, the fuel pump circuit, injector circuit/ECU, or clogged fuel system components.

The fact you got it started on alternate fuel is great.
 
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