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Issue With '87 Getting Fuel

Upstate

Upstate

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Ok, the lowdown, '87 with TBI mounted on '79 350 with the '87 intake. I bypassed the relay and the fuel pump kicks on. Crank but no fuel. Dump a little fuel into the TBI and it starts.

What am I doing wrong?
 
bypassed with key hot and CRANK HOT ?

and node light to check for injector pulse .

and tbi dist correct ? not huge cap hei still ?

then we go from there.
 
Upstate said:
I bypassed the relay and the fuel pump kicks on.
What am I doing wrong?
Click to expand...
ECM sends signal to relay to turn it on and when on another wire sends signal to ECM fuel pump is running. Not sure how or why you would remove the relay? :dunno:

Turn key on and fuel pump runs a couple seconds unless you hit Crank in which it is on, then ECM receives DRP pulses from distributor to fire injectors.
 
sweetk30 said:
bypassed with key hot and CRANK HOT ?

and node light to check for injector pulse .

and tbi dist correct ? not huge cap hei still ?

then we go from there.
Click to expand...

TBI dist in, not hei. I connected to the pigtail by the AC. Then I would turn I over and if pour in fuel not the TBI it would start otherwise no.
 
eagle mark said:
ECM sends signal to relay to turn it on and when on another wire sends signal to ECM fuel pump is running. Not sure how or why you would remove the relay? :dunno:

Turn key on and fuel pump runs a couple seconds unless you hit Crank in which it is on, then ECM receives DRP pulses from distributor to fire injectors.
Click to expand...

I did not remove the relay, just used the bypass pigtail. When I turn the key on I get no response from the fuel ump.
 
Check the whole fuel system. No fuel when you turn the key, but bypass brings it to the TBI. Still doesn't start.
 
is it an intank pump?? if so it sounds like the rubber hose in the tank broke. did it to me on my burb
 
shady said:
is it an intank pump?? if so it sounds like the rubber hose in the tank broke. did it to me on my burb
Click to expand...

Yes electric in the tank pump. Here is the thing, bypass the relay and I get fuel to the TBI, don't bypass and no fuel. I have spark fine, but injectors won't fire.
 
ah, didnt catch that. sounds like the pick up in the distributor. thats what fires the injectors.

edit; I guess that wouldnt be it either:doah: i dont know :dunno:
 
Sounds like a bad ignition module. The module gives a signal to the ECM to fire the injectors and also to run the fuel pump. You can still have spark but no signal for fuel pump or injectors.
 
4X4HIGH said:
Sounds like a bad ignition module. The module gives a signal to the ECM to fire the injectors and also to run the fuel pump. You can still have spark but no signal for fuel pump or injectors.
Click to expand...

Interesting, it signals both?
 
Sorry I was late to the party. Module doesn't run the TBI prime circuit.

Prime is handled by the ECM. It's not every time you turn the key to run, I think it's on a timer.

Check that the wire from the ECM to the relay has voltage when you initially turn key to "run". Not sure what the time is that will allow another prime cycle, but I'd guess 15 seconds or so between the on/off of the key. Since this is a retrofit, I'm going to bet the most common problem, wired incorrectly. Check fuses as well though, if not yet done. I would guess one of the power feeds to the ECM is not getting power as it should (12V run/start), although I'm not certain how power for the relay is handled within the ECM. Could even be the connector is wired incorrectly, if you had to do some re-pinning.

Big cap or small cap, still HEI.
 
dyeager535 said:
Sorry I was late to the party. Module doesn't run the TBI prime circuit.

Prime is handled by the ECM. It's not every time you turn the key to run, I think it's on a timer.

Check that the wire from the ECM to the relay has voltage when you initially turn key to "run". Not sure what the time is that will allow another prime cycle, but I'd guess 15 seconds or so between the on/off of the key. Since this is a retrofit, I'm going to bet the most common problem, wired incorrectly. Check fuses as well though, if not yet done. I would guess one of the power feeds to the ECM is not getting power as it should (12V run/start), although I'm not certain how power for the relay is handled within the ECM. Could even be the connector is wired incorrectly, if you had to do some re-pinning.

Big cap or small cap, still HEI.
Click to expand...
I have not touched the ECM the only retrofit is the motor. What are the best ways to test?
 
There are wiring diagrams for the entire EFI system at this link:
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?304-1227747-ECM-Information-42

Pin A1 on ECM is a Dark Green wire with White stripe to fuel pump relay. Test it, does it get power for 2 seconds when key is turned on? If yes replace test or replace relay. If not check power to ECM using the voltage check list.

There is also a wire called Crank Signal, check to see if that wire gets power when starter engaged.

Digatal Volt Meter is your freind! It will tell you if youi have a wiring issue or the ECM is faulty.
 
eagle mark said:
There are wiring diagrams for the entire EFI system at this link:
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?304-1227747-ECM-Information-42

Pin A1 on ECM is a Dark Green wire with White stripe to fuel pump relay. Test it, does it get power for 2 seconds when key is turned on? If yes replace test or replace relay. If not check power to ECM using the voltage check list.

There is also a wire called Crank Signal, check to see if that wire gets power when starter engaged.

Digatal Volt Meter is your freind! It will tell you if youi have a wiring issue or the ECM is faulty.
Click to expand...

Thanks, I will go through it.
 
3 things that gave me similar issues back when I was injected.

First, ignition module

Second, temp sensor that is mounted on the intake with the 2 or 3 wires, not one in head with 1 wire

Third, oil pressure sensor mounted on the back of the intake.....dont ask how long it took to figure that one out....:doah:
 
k20 said:
Third, oil pressure sensor mounted on the back of the intake.....dont ask how long it took to figure that one out....:doah:
Click to expand...
That's a redundant switch. If engine won't start because of no fuel (which the oil pressure switch is for, to keep fuel pump powered if fuel pump relay fails while driving. Oil pressure = closed switch) then the Fuel Pump Relay is also bad...

HTH!
 
eagle mark said:
That's a redundant switch. If engine won't start because of no fuel (which the oil pressure switch is for, to keep fuel pump powered if fuel pump relay fails while driving. Oil pressure = closed switch) then the Fuel Pump Relay is also bad...

HTH!
Click to expand...

Is there a way to bypass the switch?
 
Really no need to. It can't stop the vehicle from running if the Fuel Pump Relay is good.

But yes you can, just look at wiring diagrams and you will see how it is a redundant switch.
 
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