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Still need halp

Mark towery said:
Ok I may change lp this weekend. What are the factory conditions at the lp?
Click to expand...
Before changing things - unless you're upgrading anyway.

I would install a fuel pressure gauge, so you know exactly what it's doing.

I wouldn't throw that Lift pump in the garbage.
I've used a lot of lift pumps that weren't up to snuff, for other things.
They make a great little utility pump.
I've used them to clean out the bowl on a FFM. Keep adding diesel or Sea Foam until I get the bowl cleaned out
 
Jeff beat me to the punch LOL. Don't fire the parts cannon too soon. get you a fuel pressure gauge installed between the FFM and the IP to monitor pressure. (I assume you have checked the filter in the FFM) the best gauge to have is one that will also read vacuum too. but just a cheap one will do.

Harbor Freight sells a fuel pressure test kit that will work. it comes with a tee you can place inline on the hose temporarily just get you some extra fuel hose to have some length to run the gauge out to the wiper blade so you can see it from in the captain's chair.
 
JayTheCPA said:
In this case, no need for a fuel gauge that shows a vacuum. The engine lets us know about a fuel vacuum when it goes quiet 🙃
Click to expand...
I don't understand.
The engine will still run with the fuel pressure gauge showing vacuum.

Though, All the fuel psi has to do is get low and you know you have a problem that needs to be addressed
 
If measuring at the IP, every time mine went to 0 psi, the engine died. Wouldn't do much more than idle if the max pressure was below 5 psi. Could limp home if I had 7 psi, but the engine was not happy.

If measuring upstream of the LP, can see where measuring a vacuum is workable while still allowing enough fuel for the engine to run. Probably not a good scenario for the LP though.
 
Last edited:
Holy chevroly batman. First things first.

You have air bubbles in the line. That can wreck proper operation and throw off every other test. That is why GM made it the first step in diagnostics

However sucky it is- find and repair the leak. If you’re broke that means spending tons of effort figuring out where it is. If you can spend the $, drop the tank- inspect the metal lines going into the tank. Ensure the sock filter in the tank is clear of debris. Many people choose to remove it permanently. If replacing it ensure it is the diesel one not gasoline one. If eliminating it add a pre filter.
Then replace ALL the rubber line with sae30r9 fuel line and high quality clamps.

We know your fuel pressure is low. Once the air leaks are solved retest it. If it is still low 8-14 psi is Stanadyne specifications- then remove the LP and figure out how much you can invest in something- cheap means more cost long term and more problems along the way. Spend the big bucks and get the fass system with filters and solve a ton of problems at once is best. If you do this you can remove and sell the ffm for $20 or whatever they are worth nowdays.

Invest in a permanent mounted gauge at the dash is the smartest move. Use the T That tape at the ip in metal.

Get through all that nonsense before ever considering a new ip. Why? Because any of the other stuff can ruin a new ip or make it work just as bad as what you have now, sometimes worse because it will be out if time and running so bad you can’t even time it- seen this a hundred times.
 
dbrannon79 said:
Jeff beat me to the punch LOL. Don't fire the parts cannon too soon. get you a fuel pressure gauge installed between the FFM and the IP to monitor pressure. (I assume you have checked the filter in the FFM) the best gauge to have is one that will also read vacuum too. but just a cheap one will do.

Harbor Freight sells a fuel pressure test kit that will work. it comes with a tee you can place inline on the hose temporarily just get you some extra fuel hose to have some length to run the gauge out to the wiper blade so you can see it from in the captain's chair.
Click to expand...
ok and yes I took ffm off and cleaned it up real good
So DO NOT use tee valve?
Will L. said:
Holy chevroly batman. First things first.

You have air bubbles in the line. That can wreck proper operation and throw off every other test. That is why GM made it the first step in diagnostics

However sucky it is- find and repair the leak. If you’re broke that means spending tons of effort figuring out where it is. If you can spend the $, drop the tank- inspect the metal lines going into the tank. Ensure the sock filter in the tank is clear of debris. Many people choose to remove it permanently. If replacing it ensure it is the diesel one not gasoline one. If eliminating it add a pre filter.
Then replace ALL the rubber line with sae30r9 fuel line and high quality clamps.

We know your fuel pressure is low. Once the air leaks are solved retest it. If it is still low 8-14 psi is Stanadyne specifications- then remove the LP and figure out how much you can invest in something- cheap means more cost long term and more problems along the way. Spend the big bucks and get the fass system with filters and solve a ton of problems at once is best. If you do this you can remove and sell the ffm for $20 or whatever they are worth nowdays.

Invest in a permanent mounted gauge at the dash is the smartest move. Use the T That tape at the ip in metal.

Get through all that nonsense before ever considering a new ip. Why? Because any of the other stuff can ruin a new ip or make it work just as bad as what you have now, sometimes worse because it will be out if time and running so bad you can’t even time it- seen this a hundred times.
Click to expand...
thank you
 
I can't remember it the tee valve will give you a pressure reading from before the filter or after. you can use it for now in your testing, but you might be off a couple PSI since you not reading right at the IP where the fuel goes in. that is the best place to read pressure from.

what are you using to read fuel pressure currently?

And yes what Will is telling you, since you are getting air in the return line, you will need to find and fix this. this might be your whole issue causing low pressure along with the symptoms you are experiencing. Having air in the fuel lines will effect pressure too. air will compress, liquid will not.

9 times out of 10, when you are getting air in the lines, the place to look is anywhere along the steel line and rubber hose starting from the fitting at the back of the LP all the way back to the tank including the pick-up tube inside the tank. We are talking about a tiny pin hole smaller than you can see. Big-T had this issue and ended up having to replace the pickup tube assembly with the lines that connect to the tank.

Honestly if there was a way to safely pressurize the lines behind the LP going into the tank. you would find the leak right away!!

up on top of the fuel tank you can follow the steel line from the LP back and you will find there is a section of rubber hose about 12 inches from where it connects to the tank. this area is prone to leak or in our case suck air. since there is no pump inside the tank you will never see the leak. this is due to these lines never getting pressure on them. Think of it this way. your truck is a 2000 model. that means that the rubber fuel hoses on top of your fuel tank are 24 years old and going on 25. Would you trust 24 year old radiator hoses not to bust while driving across the states?
 
Mark, is this the truck in your profile pic? with a flat bed? do you have the means to lift the flat bed off the truck where you have full access to the top of the tank and the fuel lines?
 
Well I was thinking that since your truck has a flat bed and not the factory pickup bed, it might be easier to lift the flat bed off the frame and have full access to these rubber hoses going into the tank along with access to the top of the tank where the pickup tube is. you can pull and inspect easier than having to drop the tank from under the truck.
 
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