Fuel issue carb, SOLVED
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From: Virginia
A little hint. Get your meter off continuity mode. That is not telling you anything. Put it in DC mode to read 12v. But jumping the oil pressure switch out is telling us more than anything.
If the pump will not run with the oil pressure switch jumped and the key on, but you can hear the relay clicking, the next step it to put your meter on DC volts, and see if you have 12v on the yellow wire at the relay. It should be hot all the time, you do not need to have the key on. Make sure you find a good ground for the black lead of the meter.
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Ok so a quick test tells me that I have less than 12 V at the yellow wire 11.54 V to be accurate and my battery is showing 12.09 obviously because I haven't had any significant run time to recharge it. I probably didn't have the ideal ground which is my assumption for different in volts. I haven't tested the jumping the oil pressure switch with the key on / engine off yet to see if the pump runs, I'll do that in the morning. If the pump runs with that test what would next thought to be.
Edit: I noticed on one of the schematics it show an actual fuel selector relay where is that relay located?
It was homemade schematic with colors.
Edit: I noticed on one of the schematics it show an actual fuel selector relay where is that relay located?
It was homemade schematic with colors.
Moderator
Joined: Jan 2001
Posts: 56,984
Likes: 2,738
From: Virginia
Ok so a quick test tells me that I have less than 12 V at the yellow wire 11.54 V to be accurate and my battery is showing 12.09 obviously because I haven't had any significant run time to recharge it. I probably didn't have the ideal ground which is my assumption for different in volts. I haven't tested the jumping the oil pressure switch with the key on / engine off yet to see if the pump runs, I'll do that in the morning. If the pump runs with that test what would next thought to be.
Edit: I noticed on one of the schematics it show an actual fuel selector relay where is that relay located?
It was homemade schematic with colors.
Edit: I noticed on one of the schematics it show an actual fuel selector relay where is that relay located?
It was homemade schematic with colors.
If you jump the pressure switch and the pump runs when you turn the key, it's going to only be two possible problems; 1. The pressure switch is bad or 2. your engine doesn't have enough oil pressure to run the pressure switch.
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Ok sorry for the delay in reply. Had some work that needed to be done. And the truck had to be put aside for a little bit.
ok so I put a freshly charged battery in the truck reading at 12.45v
I checked the yellow wire at the relay with key off and had a reading of 12.44v.
I turned the key on and jumped the oil pressure switch and got no fuel flow and the pump did not come on. (I had the fuel line disconnected from the carb with a clear line attached and let it be on for a few and did not have anything come out)
Everytime I jump the oil pressure switch i can hear the brand new relay click/activate.
ok so I put a freshly charged battery in the truck reading at 12.45v
I checked the yellow wire at the relay with key off and had a reading of 12.44v.
I turned the key on and jumped the oil pressure switch and got no fuel flow and the pump did not come on. (I had the fuel line disconnected from the carb with a clear line attached and let it be on for a few and did not have anything come out)
Everytime I jump the oil pressure switch i can hear the brand new relay click/activate.
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I may have asked this before but I want to clarify.
Does the Key On/Engine Running power to the pump go thru the fuel tank selector valve?
I ask because this is where my problem started when the valve got jammed and was not functioning. I removed the valve and switched it back to the front.
Does the Key On/Engine Running power to the pump go thru the fuel tank selector valve?
I ask because this is where my problem started when the valve got jammed and was not functioning. I removed the valve and switched it back to the front.
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From: Virginia
I may have asked this before but I want to clarify.
Does the Key On/Engine Running power to the pump go thru the fuel tank selector valve?
I ask because this is where my problem started when the valve got jammed and was not functioning. I removed the valve and switched it back to the front.
Does the Key On/Engine Running power to the pump go thru the fuel tank selector valve?
I ask because this is where my problem started when the valve got jammed and was not functioning. I removed the valve and switched it back to the front.
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From: Virginia
Alright, I went through the thread again. What we know, correct me if I am wrong on anything;
The pumps do run during cranking correct? After that they do not run.
We do not know if the oil pressure switch is working, but when you jump it, the relay clicks but the pumps still do not run.
The relay is new.
You have power on the yellow wire going to the relay.
If you want to check something next, you can check for voltage on the pink/black wire leaving the relay. It will have voltage only when the relay clicks. If that has voltage when the relay clicks, the next thing downstream is the dash switch. If you want to try a quick experiment, take the dash switch and rapidly switch it back and forth about 10 times and then leave it on the pump you want to run, and then see if the pump runs when the relay clicks. You can jump the pressure switch again, that way you do not have to run the engine.
The pumps do run during cranking correct? After that they do not run.
We do not know if the oil pressure switch is working, but when you jump it, the relay clicks but the pumps still do not run.
The relay is new.
You have power on the yellow wire going to the relay.
If you want to check something next, you can check for voltage on the pink/black wire leaving the relay. It will have voltage only when the relay clicks. If that has voltage when the relay clicks, the next thing downstream is the dash switch. If you want to try a quick experiment, take the dash switch and rapidly switch it back and forth about 10 times and then leave it on the pump you want to run, and then see if the pump runs when the relay clicks. You can jump the pressure switch again, that way you do not have to run the engine.
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Ok so I have gone thru everything that I can possibly think of
i have powered the pump directly so I know the pump is good.
I have verified I'm pulling fuel from the front tank thru the selector valve on initial start.
my inertia switch is good (I have power at yellow on relay)
I have jumped oil pressure switch with key ON and cannot get any fuel (checked with fuel line off of carb).
If there was a fuel selector switch relay on this truck where would it be. Thats the only thing I can think of at this point.
visually looking at the dash switch (next to climate control ) when it was apart it looks to be a very basic switch so how would i test it and if this switch was bad could it cause the problem?
Does power to the pump go thru it when the truck is running?
i have powered the pump directly so I know the pump is good.
I have verified I'm pulling fuel from the front tank thru the selector valve on initial start.
my inertia switch is good (I have power at yellow on relay)
I have jumped oil pressure switch with key ON and cannot get any fuel (checked with fuel line off of carb).
If there was a fuel selector switch relay on this truck where would it be. Thats the only thing I can think of at this point.
visually looking at the dash switch (next to climate control ) when it was apart it looks to be a very basic switch so how would i test it and if this switch was bad could it cause the problem?
Does power to the pump go thru it when the truck is running?
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Ok so I tried what you said in your post.
And I do not have power to the the pink/black wire. (i want to clarify on something I have and separate pink and separate black wire however the go to the same connection on the relay).
Also when I have the key on with the oil pressure switch jumped I lose power to the yellow wire. I have a feeling this is not correct as you said it should have 12 volts at all times. Correct?
And when I have the key OFF and it not jumped it slowly raises the voltage and I mean slowly
And I do not have power to the the pink/black wire. (i want to clarify on something I have and separate pink and separate black wire however the go to the same connection on the relay).
Also when I have the key on with the oil pressure switch jumped I lose power to the yellow wire. I have a feeling this is not correct as you said it should have 12 volts at all times. Correct?
And when I have the key OFF and it not jumped it slowly raises the voltage and I mean slowly
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SOLVED SOLVED
Ok it's running and solved after several different avenues of testing and retesting.
The issue was the Inertia Switch. For whatever reason while testing it off or on the truck it shows it's good and is working however when all is said and you start the truck it fails. Also the everything was working great before I hit the tank selector switch on the dash so who knows what kicked it.
I bypassed the switch FOR TESTING PURPOSES and the engine stayed running without any issues. I will be replacing the inertia switch and buttoning up everything I messed with in the following day. But alas the truck is running and working again.
Now time to figure out what the heck is going on with the rear tank.
One final question does the tank selector switch only function and switch the tanks when the the engine is running? Cause i cannot not here it switch while the engine is not with key ON.
The issue was the Inertia Switch. For whatever reason while testing it off or on the truck it shows it's good and is working however when all is said and you start the truck it fails. Also the everything was working great before I hit the tank selector switch on the dash so who knows what kicked it.
I bypassed the switch FOR TESTING PURPOSES and the engine stayed running without any issues. I will be replacing the inertia switch and buttoning up everything I messed with in the following day. But alas the truck is running and working again.
Now time to figure out what the heck is going on with the rear tank.
One final question does the tank selector switch only function and switch the tanks when the the engine is running? Cause i cannot not here it switch while the engine is not with key ON.
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From: Virginia
I am glad you got it going. What you found out is important. Another reason to use a testlight. Are you using a digital meter? That's ok if you load the circuit down like you just found out. A digital meter uses so little current to operate, that is can lie to you. A intermittent connection will pass the very little current that a digital meter requires, but will not pass the current required to run the pump and 90% of the time will also not pass the current needed to run a testlight. But you got it.
Looking at the diagrams, the selector switch and selector valve are powered by the relay circuit you just fixed. So it's only going to work when you have oil pressure which activates the relay. So its only going to work with the engine running. You can keep testing like you were before by jumping the oil pressure switch. Easier to hear the pumps running and things clicking with the engine off.
Looking at the diagrams, the selector switch and selector valve are powered by the relay circuit you just fixed. So it's only going to work when you have oil pressure which activates the relay. So its only going to work with the engine running. You can keep testing like you were before by jumping the oil pressure switch. Easier to hear the pumps running and things clicking with the engine off.
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I was using a test light as well I was getting enough current to light it but not enough for it to run the pumps. That is what initially made me believe it was good. I am am an avid test might user myself and prefer it when working on anything 12v. Either way bouncing things ba k and forth with got it fixed and I greatly appreciate it. If your ever in oregon look me up.
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