Engine/Transmission (1994 - 1998) Lift Pumps going bad 4th one

[Stixx]

I have a buddy of mine who put a 94 12v in a 87 Ford. He cant keep a life pump in it for longer then 1500 miles. The motor lose's its prime and wont run, Typical for a bad lift pump. He has tried 2 Napa's and now just bought his 2nd from Cummins. He even put a inline fuel filter before the lift pump, but that doesn't seem to help.



Any idea's?

 

[Joe G.]

Is he SURE it's the lift pump? It may be something else like fuel hoses. My lift pump has never been touched. 212K miles.

 

[Blackcloud]

I agree with Joe on the fuel lines idea. It sounds like air is getting into the fuel system if you are losing prime.

 

[Stixx]

He can put a new one in and it runs good.



But I'll tell him about the lines.



Won't it smoke white if hes getting air?

 

[illflem]

If he's getting air it will usually start hard.

Has he checked his fuel pressure?

If it's higher than the recommended 30 psi max due to a pinched return line or bad overflow valve he may be overloading the pump and prematurely killing it. I ran into one where the return line was kinked in a clutch replacement, fuel pressure at idle was 85 psi.

 

[Joseph Donnelly]

Dissect the bad pump and see if there is rust or grit in there from dirty fuel or rust in the fuel tank.

 

[Stixx]

Here's an idea,



Its a 4 door long box ford that this 12v is in. Dont the extended cab CTD's have a pump in the tank?



I think he's working that lift pump too hard on that long fuel line. Causing it to wear out.

 

[KSyme]

Has he ever taken the lift pump apart to see if he can find the problem? My engine would rev up to a certain speed then blow white and kinda stay at that RPM. This always varied as to what temp the engine and fuel was. Cold was bad, hot was alot better. Well I finally ordered a new lift pump and suction hose from Cummins, took my old pump off ond removed the plunger and check valves and the check valve on the outlet had a broken spring and messed up seat. I noticed before that when I changed fuel filter that the fuel at the bleeder would raise up and down when the primer button was being pushed. The new lift pump cured my white smoke and rev. problem.

He could also tee in a fuel pump testing vacumn gauge in the line before the pump just to check if there is excessive suction between pump and tank.

 

[KSyme]

Just another thought, has he tried blowing back into the tank from the pump suction hose? It my be possible that the suction sock (plastic screen) in the tank is sucking full of debris and the vacumn is holding it choked off until he unhooks the fuel line and changes the lift pump????????????? Does that 87 have 2 tanks?

Just might try plumbing direct to one tank and bypassing valve.

 

[pwknapp]

Got to be something other than the pump itself. I've got 430K on my original lift pump but have had to change the lines. (I do carry a spare in the toolbox. )

 

[JohnE]

Its not the length but the diameter of the fuel line to consider

If the 87 Ford was a gasser the fuel line is grossly undersized. If it was a diesel, the fuel lines are undersized.



Here's an area comparison chart of line diameter versus area

1/8" line = 0. 01 in<sup2>

1/4" line = 0. 05in<sup2>

5/16" line = 0. 08in<sup2>

3/8" line = 0. 11in<sup2>

1/2" line =0. 19in<sup2>



The pre-filter is a bad idea, too.

 

[redram]

Originally posted by Stixx

Here's an idea,



Its a 4 door long box ford that this 12v is in. Dont the extended cab CTD's have a pump in the tank?



I think he's working that lift pump too hard on that long fuel line. Causing it to wear out.

No in tank fuel pump in a CTD on any 12 valve that I've seen in either the 89 or 96 that I own or used to.