About to strike a match

[englewoodcowboy]

Well As in my other thread, I finally got the little ranger running only to have it quit again today. The fuel pumps again are not running. The relay closes when you turn on the ignition but the pums do not run. The rear pump is brand new. The relay has 13.0 volts and when the relay clicks it passes 13.0 volts then a second or two later it clicks again and there is 5.0 volts on the line. Fuses are good, I'm running out of ideas. I'm leaning towards a bad ground or a shorted out pump.

 

[Mark_88]

did you check the inertia switch? It is designed to kill the fuel pumps and can be shorted out or otherwise just wonky...up under the dash on the passenger side...can be bypassed with a U shaped wire to test...

 

[alwaysFlOoReD]

I thought the inertia switch was on the pass. side floorboards under the rug beside the trans tunnel.

Richard

 

[Mark_88]

I thought the inertia switch was on the pass. side floorboards under the rug beside the trans tunnel.

Richard

Somewhere thereabouts...mine, when I had one, was just beside the tunnel but attached to the firewall...

 

[adsm08]

So far everything he has described sounds normal to me. The key is turned on, the pumps get priming signal for a few seconds, then they get shut off until the engine starts to spin.

Prove to me that the pumps aren't running. Do a fuel pressure test.

 

[englewoodcowboy]

No pressure from the pumps. At the pump I'm not getting any power. The relay closes and sends power (tested at the relay) but its not getting to the pump and what has me boggled isthat when the relay switches off I get a 5vdc on the line. Where is the fuel pump inertia switch wired in the series, before or after the relay? I hate to say it but as in my last issue, I, well my son and I were 100% the cause of he regulator failure due to a kinked line when we reinstalled the tank. Now we are back to the origional problem we had when we were lead to a bad in tank pump. I know it was 100% bad as I suppled power to the pump whenit was out of the tank and it is dead. The repacememnt pump fired right up. Now we are at the fuel pumps not working again and this time it stranded us on the top of a mountain on our neighbors farm while we were cutting fire wood for next year. I know I am fried with working on it and equally fried having to hitch my gooseneck trailer and go retrieve it.... Sorry for the rant.

 

[adsm08]

If you stick your head in front of the passenger seat the switch should be on the fire wall, halfway between the trans tunnel and the outer wall of the car.

 

[englewoodcowboy]

Are the switches known to go bad or trip easily?

 

[adsm08]

They have been known to wear out and trip easily or have the contacts go bad.

 

[a31ford]

OK, I think (Think) I have this one......

Ground (NOT Power) wire is the problem.

Having a voltage there when the pump is NOT running, is the thing, remember the turn signal light that flashes only when the running lights are off ? it's because the ground at that lamp is missing, so the turn filament is finding ground THROUGH the running filament.

Try adding a ground wire AT the fuel pump from the FP's ground (Do NOT assume, verify the ground OR you might BLOW your self to kingdom come) !!!

And add a ground to a KNOWN GOOD Ground point (Like a long wire back to the battery, (for testing only)).

IF this does the trick, then find a good point on the frame or such.

Greg

 

[englewoodcowboy]

As of right now we think it was the inertia switch. The contacts had to get warm as the plug and socket were partially melted. The second we bypassed it o test the pumps fired right up. Fingers crossed this is it for a while. Im also restorng an 87 BII and thinking I might get a new switch for it to be safe. Any thoughts?

 

[adsm08]

Don't fix what ain't broke.

 

[AllanD]

It is the ignition "Tach" pulse back to the EEC that tells the EEC to keep the fuel pumps powered, so if that signal lead is compromised the EEC does not keep the pumps powered.

 

[trail B2]

I had an intermittent fuel pump problem also.Long story short it was the nut that holds the main power line into the fuse and relay box.I took out the box rolled it over and underneath you can see the nut took a while to figure out that one.

 

[englewoodcowboy]

Funny you mentioned the tach. The tach doesn't work and I'm trying to figure it out and the horn. The tach moves a little when you turn the key on and there is a signal on the green/yellow wire from the coil.