Engine/Transmission (1994 - 1998) fuel pump sucking air, out of ideas

[GAmes]

When it rains it pours. Fishing was pretty good, but when I got back to the ramp today all I got was a click when I turned the key All this crankin' killed my starter. I got pull started by a Ford, whose owner told me I couldn't bad mouth his 6. 0 anymore:-laf So until I get the starter fixed I'm dead in the water for troubleshooting the fuel system.



I will figure it out though.

 

[hsmith]

Too bad the kind fellow with the 6. 0 will never see a no start at 700k on his. Glad the fishing was good. Kinda takes some of the sting out of knowing you still have a problem to solve. Let us know what it is.
I've been needing to replace my front crank seal for some time. Good project for today or tomorrow. Depends on what the tee times are!!!

 

[GAmes]

I pulled the starter and it is beyond rebuild. I'm ordering a new Denso. Until it arrives I have a hobby pickup to pull the boat. With forecast temps in the 70s and the grandsons out of school on break guess it's FISHING TIME

 

[fest3er]

I pulled the starter and it is beyond rebuild. I'm ordering a new Denso. Until it arrives I have a hobby pickup to pull the boat. With forecast temps in the 70s and the grandsons out of school on break guess it's FISHING TIME

Isn't that a little chilly down thataway?

 

[GAmes]

Isn't that a little chilly down thataway?

No, I'm not in south TX. We actually get snow and freezing rain every once in awhile this far north.



BTW, thanks for the illustration about how the return line could cause hard starting. Never thought about it siphoning fuel out of the injector pump.



So today, since the starter was out of the way, I disconnected the supply hose from the hard line and pressurized it with about 15psi. The plan was to spray soapy water on all the components I've replaced, then if there was no leak to pressurize the return line. No need for soapy water. Fuel immediately began to spray out of the threads of the elbow fitting that goes into the pump. I had tightened it gutntite and lined it up for the L shaped hose. Another removal of the assy and into the vice. It took a 2 foot cheater to get the fitting to make one more revolution but it doesn't leak air now. Oo. Everything is back together and waiting on the starter. I'm wondering if I clean the reduction gears with brake cleaner, then soak the bearings with PB Blaster if the starter will work for one more start:-laf

 

[fest3er]

No, I'm not in south TX. We actually get snow and freezing rain every once in awhile this far north.



BTW, thanks for the illustration about how the return line could cause hard starting. Never thought about it siphoning fuel out of the injector pump... .

YW.



I recall driving from Clovis up through Armadillo in '85 or so after an overnight flurry. It wasn't much more'n 10F, the wind was blowin' good, and the snow was packed a foot thick on the highway, with chuckholes in the snow, of course. IIRC, it took me 4-5 hours to drive 40 miles in my tinny little 200SX; I couldn't get around much of the poky traffic.



Down where you are, we New England Yankees would be basking in the sun at 50F.

 

[SMorneau]

I didn't see where this was done or suggested, have you pressurized the fuel tank with very low pressure while checking the entire system for leaks?

 

[GAmes]

I didn't see where this was done or suggested, have you pressurized the fuel tank with very low pressure while checking the entire system for leaks?

Yup, three posts ago I pressurized the components I replaced and found a leak. I'm waiting on a new starter. Mine is dead. I'l find out then if fixing the leak I found will fix the problem. I'm sure that it will. Thanks anyway.

 

[GAmes]

It's fixed!!

Oo. Oo. One more turn if the elbow fitting between the pump and the prefilter is all it took. One more thing to add to the list of culprits that can cause hard starting after a pump replacement.



I bought my new Denso starter here. Yard Truck & Diesel Parts Specialists. FLEETSOURCE: A complete transportation industry provider. That is about $140 less than Fostertrucks.

 

[SCClockDr]

Glad to hear it, GAmes. Congratulations!!

 

[KCanepari]

glad to hear you found the leak. Any leaks before the lift pump will cause no start or poor running condition and white smoke. any leaks after pump will cause hard start, but will run fine once it's going. One time just my fuel filter loosened up.

 

[ewcmr2]

Any leaks before the lift pump will cause no start or poor running condition and white smoke. any leaks after pump will cause hard start, but will run fine once it's going.

So what causes low power after using lots of power?

 

[GAmes]

Any leaks before the lift pump will cause no start or poor running condition and white smoke. any leaks after pump will cause hard start, but will run fine once it's going.

I don't know where you got that but the first statement is not true. Once I got the engine started it idled normal, had full power and ran great, even while towing the boat, and the exhaust had no color once the engine warmed up. I'm assuming you are talking about an air leak in the return hose in the second statement and I agree. If you are talking about a fuel leak between the fuel pump and the injector pump the smell of diesel will run you out of the cab in a heartbeat.

 

[ewcmr2]

So what causes low power after using lots of power?

Bad lift pump. Apparently the p7100 can suck fuel out of the tank without much help from the lift pump.



My truck would start/run/drive well as long as I didn't go past 1/2 throttle. If I went past 1/2 throttle it would accelerate hard for a couple seconds then stumble/cough not make any power.



I set up a fuel pressure guage and found 3psi at idle and 0psi when revved up. When I removed the old pump the plunger was "pushed in" and didn't pop back out on it's own. I disassembled the old pump to find the main spring in 4 pieces.