Fuel Pump Install Problem

[Ronnie9000]

Howdy folks--

My 1990 F350 wouldn't start the other day. I had changed the fuel filter about a week earlier and driven very little since then (<10 miles probably) with no issues. So at first i suspected something was wrong with my filter install. I had zero pressure at the schrader valve. I opened the fuel line going into the fuel filter (the line coming out of the pump) and turned over the engine, expecting to get fuel spray. But i got nothing. So i thought perhaps it was the fuel pump. I verified that there was no obstruction in the lines up to the pump, so there was nothing else but the pump to change.

I bought a new mechanical fuel pump. Since then I have reinstalled the pump FOUR times, each time checking to see if it would pump fuel and each time being disappointed. at first i thought i wasn't positioning the cam correctly, but i have turned the engine over multiple times to verify that i am definitely getting the pump arm under the proper lobe.

Could it be that the new fuel pump is faulty? I know that it can pump fuel, because i put it in a vise and manually pumped fuel through it pretty easily. But i did notice that there is more side to side play in the new pump arm than in the old one--could it possibly have enough play that it is slipping off the lobe and riding on the non-lobed cylindrical part of the cam? Has anyone experienced a similar issue?

 

[Oledirtypearl86]

How much side to side play I have a new one I keep on hand it has about 1/8inch play on it and it could just be a bad one off the shelf I know they take the old ones as a core for rebuild I wonder if you got a core and not a new/rebuild also have you looked at the lobe to make sure there is still a lobe there?

 

[Ronnie9000]

Hey Oledirtypearl86-

I guess i'll have to pull it off the truck one more time. When i do that tomorrow I'll compare the play between the old and the new and report back.

Thanks!

 

[Oledirtypearl86]

Hey Oledirtypearl86-

I guess i'll have to pull it off the truck one more time. When i do that tomorrow I'll compare the play between the old and the new and report back.

Thanks!

Yeah let me know and there should be some spring tension on the install I use studs and just have to put the nuts and washers on to install also check your oil see if it smells like diesel if it is a bad lif pump could be pumping fuel into the crank case also repriming the fuel system can be a pain it can take a bit of cranking

 

[chillman88]

Have you verified the tank selector valve isn't stuck? Happened to me last year. Are you over 1/4 tank of fuel so you know you're actually getting fuel? If the pick up in the tank fell off you won't get fuel under 1/4 tank.

Welcome to Oilburners!

 

[RDieselKid84]

Hey just put a little pressure on the tank you are using and see if the fuel comes out at the pump supply line. That will let you know if you have a restriction.

 

[IDIBRONCO]

have you looked at the lobe to make sure there is still a lobe there?

The lobe can't fall off of the camshaft. If it was there and working before, it should be now. There's a half moon shaped key that goes in the cam to keep the fuel pump eccentric lined up. It also keeps the cam gear in proper time.

 

[Oledirtypearl86]

The lobe can't fall off of the camshaft. If it was there and working before, it should be now. There's a half moon shaped key that goes in the cam to keep the fuel pump eccentric lined up. It also keeps the cam gear in proper time.

Lol I know the lobe isn't going to fall off but if you look and check you might notice something you didn't before

 

[Ronnie9000]

Hi everyone--

I haven't had a chance to take off the pump and look at it again. I'm fairly sure it's not a fuel selector valve or line obstruction, because I actually unhooked the main fuel line and connected a 2 foot length of fuel hose to the pump intake and ran it into a can of diesel right by the pump and tried to get it to work. Nothing came through. I figured that should be able to pull fuel through pretty quickly if the pump was working correctly, shouldn't it? But nothing happened.

I hope i'll get home from work tonight in time to get the pump off and check the play in the arm. I'll take pics and upload them when i do.

Thanks again!

 

[gfemling]

Another possibility is the lobe of the eccentric being worn down. When I overhauled my 6.9 w 250k mi, the eccentric was pretty warn down- was still pumping but who knows how efficiently. Suspect would need to be pretty severely worn not to pump with new mechanical pump but if all else fails to explain, may be worth examining with a mirror or borescope

 

[Ronnie9000]

I finally got around to pulling off the new fuel pump. Here's what i found in comparison:

old pump: side-to-side play in the arm was .028"
new pump: side-to-side play in the arm .071", so roughly 2.5 times the play of the old one.

Or about 1/32 compared to 5/64. In comparison that's a lot more slop than the previous pump, but i don't know if its enough to give it room to slide off the eccentric lobe? The lobe itself doesn't look terribly worn, but then again i might not be the best judge of this. I can't take pictures at the moment (phone died) but I will try to get a pic of the camshaft lobe soon. In the meantime, i suppose i'll take the new pump back and try to swap it.

Another question--how long do yall think it should take cranking to pull fuel through a two foot length of hose from a bucket of diesel to the outflow of pump (not even up to filter, just immediately out of the pump), as i described in an earlier post? I just want to make sure that i'm being patient enough with the pump, in case it is very slow.

 

[Ronnie9000]

Update: I just got another pump, it has practically no play in the arm. I put it in the truck, and fuel pumped through within 5 seconds of cranking. So i guess it was the pump after all. Thanks everybody for your help!

 

[Oledirtypearl86]

I'm glad you got it figured out nothing g worse than getting new parts that are broke