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Fuel pump problem...what else to try?

M

Midwestblue

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Truck is an 89 K5 with 350 TBI--the motor was just put back in and I haven't been able to get it to start.
The problem is no fuel...I used the test lead on the fuel pump relay and gave it 12 volts and the fuel pump kicked on so that is not the problem. But I can't get the fuel pump to work by turning the key. Nothing happens, I put a test light on the wires on the tank with the key on and nothing. I also replaced all of the fuses, so that is not the problem. Where do I go from here? Is there a ground or an in-line fuse? I'm so close to getting it running again /forums/images/graemlins/frown.gif
 
If you can't find the problem hot wire the fuel pump to the relay through the igniton on a hidden toggle and you would also have a theft deterent. /forums/images/graemlins/thumb.gif
 
I'm about to take that route! I'm getting frustrated with this thing /forums/images/graemlins/angryfire.gif
 
Fuel pump relay may be bad. It would keep it from sending power to the fuel pump with the key on. They are like $10 at your local parts house.

Harley
 
I replaced the fuel pump relay...still not working. When I give the test lead power, fuel gets to the throttle body but it won't come out the injectors, even with the key to the "Run" position.
What else can I do?
 
If I'm not mistaken, you won't see fuel unless it's cranking.

Guaranteed there is a troubleshooting chart for fuel delivery problems in the factory service manual.
 
Do you have power to your radio and other things? I bet your fusable link may be bad. There is a chance that you either got it pinched between the engine and tranny when you where installing the engine or it got pulled on too hard and the fusable link wire broke inside. If you don't know where this wire is, it goes from the starter to the ignition switch. This wire is what supplies power to the igntion switch which will control everything attached to the ignition switch including the ECM, and all it functions which means fuel pump, injectors and such. /forums/images/graemlins/thumb.gif
 
I have power to everything and I checked the fuseable link just in case and it is okay.
Would a bad oil pressure sensor/switch (whatever it is called that is right by the distributor) cause the problem?

I will check the ignition module, (I do have spark) but I probably should have replaced it since I replaced most of the rest of the ingnition stuff already.
 
i second the module. had same problem with my 90 blazer. the ignition module also sends a signal to the ecm then the ecm sends a signal to the injectors. i still had a spark with the old module.
 
I could be mistaken, but if I'm not, the ECM is what commands the fuel pump on for 2 seconds, regardless if there is oil pressure or the engine is cranking.

If you aren't hearing the pump for the 2 seconds when the key is turned to run, I don't see the correlation between the ignition module and the fuel pump problem.

You should be able to check the module by putting a test light across one of the injector connectors. Since the module "tells" the ECM the engine is cranking, if the test light doesn't blink as someone cranks the engine, then I'd look at the module.
 
You can have the module tested for free at Autozone. The ECM actually sends ground signals to the injectors to get them to fire. Again, as I said before, check for good grounds to both the ECM case and the engine block itself. But if the ECM won't fire the fuel pump... very odd.

You don't get any error codes from the ECM? Does the SES light come on with IGN the key in the run position?

Check these out:

http://64.53.225.17/images/truck/EFIconv/wiring/ChartA-1.JPG

and

http://64.53.225.17/images/truck/EFIconv/wiring/ChartA-1a.JPG

These should help if I remember right, these are what I went off of when my first homemade EFI setup didnt fire.

Hope I've helped again! /forums/images/graemlins/wink.gif

-Dan
 
Also, did you get a chance to hook up WinALDL? Did it show any sensor data? Any info come up at all?

Thx,
-Dan
 
I checked the green wire with white stripe on it on the relay it should have power for 2 seconds after the key is turned on--No power to it. And I checked the orange wire which is supposed to have power continuously with the key on--No power to it either. I haven't checked the ignition module yet--If it's bad would it keep power from getting to the fuel pump relay?

Everything in the truck has power except the headlights/tail lamps. The turn signals and brake lights work fine /forums/images/graemlins/dunno.gif

I'm not getting the SES light and no codes
 
Sounds to me like you lost power to the ECM somehow... Check for power on the appropiate pins according to the diagrams I attached to the old thead on this subject. You can check my site and get them there too.

-Dan
 
That is pretty much the only thing left that could be wrong...I replaced the ignition module and the injectors still won't fire.
 
[ QUOTE ]
And I checked the orange wire which is supposed to have power continuously with the key on--No power to it either.

[/ QUOTE ]

Sounds like your problem, right there.

The orange wire is ECM B on the fuse box. It powers the relay, the oil pressure switch and the ECM. It should have power to that line as long as the fuse is good. It would not matter if anything was bad, like the ignition module.

If the fuse is good, check for power at the ECM in pinsC16 and B1.


The following is AFAIK -

I suspect that wire has gone bad somewhere. The relay is only to power the 2 to 10 second prime. After that, the oil pressure switch supplies power to the fuel pump.
But, if the orange wire has no power at all, the relay or the oil sender will not power the fuel pump.
 
Here is another thought:

Are your headlights suppose to be working?

If so, maybe the main power strip portion of the fuse box that powers those, also powers ECM B. You may have a problem getting power to the fuse box. Did you hook up the power connector, correctly, on the firewall? IIRC, there is a couple connectors there. Maybe one is broke or not hooked up...


Just a thought...
 
[ QUOTE ]
Here is another thought:

Are your headlights suppose to be working?

If so, maybe the main power strip portion of the fuse box that powers those, also powers ECM B. You may have a problem getting power to the fuse box. Did you hook up the power connector, correctly, on the firewall? IIRC, there is a couple connectors there. Maybe one is broke or not hooked up...


Just a thought...

[/ QUOTE ]

or the fuseable link to that side of the fuse box
 
I'm sorry, bear with me, I'm about at the limit of my electrical abilities here...I have power to this wire with the key "on"---What is this wire? The wire is either pink with black stripe or red with black stripe I can't really tell. The pin on the connection is labeled "B"
47Wire1.JPG
 
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