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87 K5 no fuel

Kota4bye

Kota4bye

1/2 ton status
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Put my steering column back together last night, and took the truck for a drive. Drove fine for 15 min, pulled in the garage and it died. Won't restart.

the fuel pump is not kicking on when I roll the key to run, but if I bypass the relay the pump runs.

Just threw in my spare ignition control mod and no change....
 
Sounds to me like the relay is toast. Got any more of the same relays laying around you can swap to verify?

I made sure all my relays are interchangeable just for this reason.
 
Ugh electrical problems. I agree with the relay thing though.

On the bright side if its a simple problem we got a guy that is coming with me on Tuesday who knows electronics really really well :doah:
 
Is the fuse good?

If the relay works, but pump does not run, and bypassing the relay "fixes" the problem, the only issue can be lack of 12V to the relay on the feed side.

Power comes from battery to relay (and to the oil pressure switch). When relay closes (ECM 2 second prime, engine running/ECM control) power is sent to the pump wire.

If relay fails, the oil pressure switch, wired in parallel with the relay, at ~4PSI closes and sends power to the fuel pump.

Since the pressure switch is wired in parallel, if the 12V feed is not working correctly, neither component will feed the pump.

You can check for 12V to the oil pressure switch (don't have the diagram in front of me) and one wire is either hot at all times, or hot in run.
 
Crap Crap, so pump kicks on if you bypass the relay but even after replacing the relay no fuel?

If you bypass it will it still kick on
 
Ok, so I'll start chasing wires this eve.

Yes bypassing relay, pump runs.

Ecm1 and ECM2 fuses good
 
Ok, noticed that I don't have a ses light when I try to start the truck, or headlights......I have 12volts at the junction block in the firewall....

I've bypassed the fusible link from the starter. Is there another one I'm missing?
 
I believe all these trucks had two fusible links. I *thought* they both fed the junction block on the firewall (drivers side, up high) but they obviously cannot, so there must be another one. Sorry I can't point to where specifically. But check the junction block, near it, and the firewall fuse panel connector.

The image I have in my head is of fusible links all being near a connector, not halfway along the wire run.
 
dyeager535 said:
I believe all these trucks had two fusible links. I *thought* they both fed the junction block on the firewall (drivers side, up high) but they obviously cannot, so there must be another one. Sorry I can't point to where specifically. But check the junction block, near it, and the firewall fuse panel connector.

The image I have in my head is of fusible links all being near a connector, not halfway along the wire run.
Click to expand...

Right.

I don't have the schematic I front of me, but there are two orange wires (b1 and c16) that should be getting power through ecmb, but are not, but fuse is still good
 
I can probably check my '91 diagram when I get home, I don't believe they changed a whole ton since then. But may not be a whole lot of help since it doesn't tell you WHERE in the engine bay it's located. At least I don't think the '91 does, the '88 Camaro manual has a diagram where some connectors is located.
 
I think I just found it. From the junction block to the bulkhead connector there is a 16 ga fusible link.

If this doesn't do, idk what I'm going to do.
 
Ok, so no change after I swap on new fusible link, but the PO had an alarm/remote door locks in the truck so

I messing with the wire bundle and the flashers start going as if the alarm was active, I turn the key to run, and the fuel pump kicks on everytime the flashers light up.....turn headlight switch on, same deal, in sync with te flashers....

So tonight I will yank the alarm and try and figure out how the wiring goes back together...fml, that will be a mess.
 
Removed all the alarm crap, still don't get a SES or fuel pump kick on in the run position.
 
I'd focus on the SES light issue. Have we verified the bulb is good?

The Chevythunder website has the "no SES light" flowchart.
 
dyeager535 said:
I'd focus on the SES light issue. Have we verified the bulb is good?

The Chevythunder website has the "no SES light" flowchart.
Click to expand...

light is good,I saw it flash last night.

I've used the flow chart, ECM is not showing voltage on B1 or C16....all fuses are good, and I think I've replaced all the fusible links now...I still don't get anything.
 
Kota4bye said:
Put my steering column back together last night, and took the truck for a drive. Drove fine for 15 min, pulled in the garage and it died. Won't restart.
Click to expand...

I'd be loooking at the switch on the steering column, not the key, the one down below with all the power wires...
 
I would change the temp sender that go's to the computer on top of the manifold. that seems to be a common but overlooked problem
 
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