I'm having a heck of a time with this bugger.

I have a 1990 E350 box truck, one pump is under the cab, I beleive there is another in the tank?

Anyways, I have replaced the relays, checked the fuses ( none of them seem to be for the fuel pump ? ) and still no power to the pump.

I have a battery pack hooked up to the front pump and it pumps.. still trying to get it to start however, I'm assuming that both pumps need to be running for it to work properly.

The battery is charging for now and will give it another go in a bit.. however.. I'd prefer not to have rig the pumps for 12v with an in cab switch..

Any alternatives?

I have no clue where the inertia switch is.. can't find it anywhere.

Any other relay/fuses, ideas?

I have plenty of spark.. need fuel!

-BT

 

I have no idea if yours is in the same place, but in my 94 pickup, the inertia switch is behind the kick panel on the passenger's side.

Good luck

 

Yes you have a low pressure pump in the tank and a high-pressure pump on the frame.

No there are no fuses in the fuel pump circuit but there is a fuse link attached to the starter solenoid and if it is like the 89 it is right behind the headlight on the passenger's side.
Try to stretch the fuse link and if it stretches it is bad.

The key must be on to enable the PCM Power relay to give power to the coil of the fuel pump relay.
The fuse link must be good to give power to the contacts of the fuel pump relay.
The PCM computer must ground the coil of the fuel pump relay for the contacts to send power on to the inertia switch.
The inertia switch must be reset to let power to go to both fuel pumps.

That is were the inertia switch is on an 89 E-series (behind the kick panel on the passenger's side) and I would think that the 90 would be the same.
Push the button down on top of it and see if it resets.

Here is a diagram.


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Thanks for the help, since we last spoke I traced every wire and cleaned every connection I could find!!

I did manage to find the inertia switch.. the button is 'in' and won't do anything when I push on it.. I did try using a paper clip to by-pass it, I also tried by-passing the oil sensor.

How much power should their be to the pump? at the connection before the pump there is 1.7-1.8 volts.. as soon as the pump is connected it zero's out.

I have 12v wired to it now and it sounds good. However the Brown Relay gets warm?

If this continues to be a pain in the *** I will just wire a dedicated circuit with a switch under the dash! I did replace the green relay, I might replace the brown as well if you think I should.

How much gas is needed in the tank for it to run? stupid question, but I've put about 10 gallons in it and it's not even to "E" yet!

I'll get another 5 gallons tonight ( at 20 bucks .. ugh ) and see if that helps..

any other ideas?? I'll check the fuse link - can I by pass it for now?

 

Well another 5 gallons of gas in the tank ( about 12-15 in there now ) gauage is just now nudging the "E" mark.. topped off the oil, charged up the battery.. hot wired the fuel pump.. turned the key..

Got a couple pops and that was it.. checked.. still have spark.. I can hear the pump running, I can hear the fuel flowing.. but it just wont run?!

Is there anything that would cause the injectors not to fire?

What is the group of 3 electrical boxes to the right of the coil.. some vacum lines and such.. the one box that is pointed to the front of the engine has a couple iffy wires.. ?

 

Try grounding pin #6 of the DLC (aka test connector) with the key on and see if the pumps run.





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I'll go and give it a shot!

btw the pink vacume line in your photo, it is severed on mine! what is it for?

 

I tired to ground it, it was pretty cruddy, worked around till I had a solid contact and grounded it out, nothing happened.

I do have a tester that will plug into that, should I see if I can read any codes?

 

how much juice should be on the fuel pump?

How much should be at the inertia switch?

How much should be at the relay? ( and which wires to meter? )

Where is the PCM and what lines to it should have juice ( and how much? )

I'm going to work my way back to the fault if I can.

I don't think my fuel injectors are firing either... ugh.. and I have a brake line to fix too.. I did check the fuseable link.. I can't pull on it, so must be good?

 

That is not a vacuum line, that is the STI connector.
When the key is turned on and it is grounded the computer will start the KOEO self test. Also the wire color is white with a red stripe.

The larger pink in the photo is a red battery cable.

I take it you are talking about pin #6 of the test (DLC) connector. If you ground it with the key on and you do not hear the fuel pump relay click then you do not have power to the coil of the fuel pump relay. This could also mean that you do not have power to the injectors also as the power comes from the same relay, the PCM power relay the one you are calling the Brown Relay.

This Brown Relay must click when you turn on the key or you will not get any fuel, the injectors will not fire and you can not run the self-test.

As I said if the Brown Relay is not clicking your tester will not work.

You will have battery voltage when all of the fuel safety devices are working giving the pump power.
Do not worry about voltage, use a test light for all of these tests and not a meter and we will get it going a lot faster.

Again batter voltage, the same as the question above.

With the key on you should have battery voltage at the input to the coil on both relays.

The PCM would be either under the heater or near the center of the dash, both places are inside the van but you have to unplug them from under the hood. If it is under the heater after you unplug it you have to take it out from inside the van.

Do not do any test on the PCM wires yet, you need other things to work first.

If you looked at the wiring diagram above you will see three fuse links, all three must be good for the fuel pumps to come on and the one for the PCM power relay must be good for the for it to work but if it is getting hot this link (located in front of the steering column) must be good.

I do not know what type relays you have so I will post a diagram of both types that you may have so you can check them. Again use a test light with a bulb for all of the tests.


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I'm checking now, btw it only gets hot when I have the fuel pump rigged on.

 

I used a light bulb tester on the /control current and / power current , nothing light up?

 

I tried the same test on a brand new relay I got yesterday and nothing light up either.. I must be doing it wrong?

My old ones are like the one shown in the bottom photo, the new one has an extra plug on the bottom to the left of the single one. ( for a total of 5 plugs )

 

How about I see if I have power to the relays instead?

I'll try to figure out which plugs to check.

 

PS what is the green relay for?