Fuel pump wont kick on

[rangeron33s]

Ok so I swapped my 2.9 in my 88 for another 2.9. Before the swap the fuel pump worked fine. I would turn the key to run position and hear it kick on and gurgle and prime. Now I'm wanting to start the new motor for the first time and nothing. Not kicking on at all. The only thing I haven't tried is using a voltmeter to see if there's power going to the pump. Is it possible that a fuel pump can go out just from sitting for 7 months?

Sent from my SAMSUNG-SGH-I997 using Tapatalk 2

 

[Spott]

Get out your volt meter. You need to figure out what is actually happening, not merely guess at what might possibly be happening.

 

[adsm08]

Agreed. It's volt meter time.

Think about it this way, you have just had 95% of your engine bay apart. No matter your skill level you can't just assume you did everything correctly and didn't miss a plug or something. And if you find something left unplugged I would assume there are more. Heck, I did two engines last summer and managed to leave the alternator harnesses unplugged from the main harness on both of them.

Each problem needs to be approached individually, not systemically (don't assume one root cause is the source of all your issues), and diagnosed with the same simple approach. SSCC. Symptom, system, component, cause.

Your symptom is the pump doesn't work.

Systems involved is pretty much just the electrical system.

Components could be wiring, relay, or the pump itself.

Now you need to find the cause. I would start by checking power. Don't just check for voltage, if it reads 12V hook up a headlight bulb in place of the pump and see if it comes on with the key is cycled. If it does replace the pump. If not, look at the wiring closer.

 

[rangeron33s]

I'm out picking up the meter rite now. Gonna test it when I get home. Will be back with results

Sent from my SAMSUNG-SGH-I997 using Tapatalk 2

 

[RonD]

Power goes like this:

Battery + ----------Fuel Pump Fuse-----Fuel Pump Relay------Inertia switch-----Fuel Pumps

1988 should have 2 fuel pumps, one low pressure pump in the gas tank and a high pressure pump in the frame rail, both are powered from the 1 wire coming out of the inertia switch.
Inertia switch is usually behind the passenger side kick panel.
Fuel pump relay gets 12volts from EEC relay when key is turned on
Fuel pump relay is activated by the computer Grounding it

'88 may have fusible link instead of a fuse for fuel pump power??

EEC relay and fuel pump relay on an '88 should be on the passenger side wheel well, green base is Fuel, Brown base is EEC

 

[rangeron33s]

There is no fuze in the fuse panel for the pump. Where is the relay at? Nothing in the fuse panel for the pump at all.

Sent from my SAMSUNG-SGH-I997 using Tapatalk 2

 

[rangeron33s]

Well I'm not really sure how to read a voltimeter or what wires on the fuel pump to test. Nothing happend with 2 of the wires key on and off and with the other 2 wires the voltimeter started jumping numbers (key on and off) I tested each wire with the positive and then had the negative on the frame rail

Sent from my SAMSUNG-SGH-I997 using Tapatalk 2

 

[adsm08]

It is often hard to test fuel pump power with a volt meter. They don't react fast enough. The fact that the meter started to jump around means you did get the plug though.

I would get a headlight bulb hooked up in place of the fuel pump and hit the key.

 

[RonD]

Set Volt meter to vDC, if there is a choice of voltage use 20voltsDC, or next higher one.

Test voltmeter at battery first, should read 12.3vDC to 12.8vDC

That is what other 12v wires you test should read.

Seeing as how pretty much everything on the truck is metal you would think the battery Ground cable going to the engine block would cover you on grounds, it doesn't.

Engine and trans sit on rubber mounts
Body and frame are bolted together with rubber grommets AFTER both are painted separately........

There should be a ground strap from engine to firewall and from engine to Frame.

There should also be a smaller ground wire from the battery to the Rad support(for the head lights).

 

[rangeron33s]

Ill try that tomorrow. How would I go about hooking up a headlight bulb?

Sent from my SAMSUNG-SGH-I997 using Tapatalk 2

 

[RonD]

Test for power at the inertia switch

 

[rangeron33s]

My confusion is which wire to test. The idiots who had the truck before me jerry rigged a trailer light plud into the fuel pump wiring. I mean its smart but the wire colors are different. I unplugged the plug and just tested each prong.

Sent from my SAMSUNG-SGH-I997 using Tapatalk 2

 

[RonD]

Should be a Pink/black stripe wire

 

[rangeron33s]

Thanks. Ill check it out more tomorrow after work.

Sent from my SAMSUNG-SGH-I997 using Tapatalk 2

 

[burn0ut]

you have looked at the fuel pump cut off switch? interior passenger side, roll the carpet or matt back and you should see it again the firewall