How much pressure does the in tank pump put out

[Bloodhound]

I have a friend that just almost stole a 90 F350. It has a 351W that has had the fuel injection deleted. They used the factory pumps and put a regulator on it with a return line. He is having fuel problems.

I was wondering if the in tank pump alone would have enough pressure to run a carb motor?

If it was mine I would put a after market pump on it. He is trying to get by the cheapest that he can.

 

[CowboyBilly9Mile]

Specs I've got are for 1991-96 models:

5.8 and 7.5L are all 35-45 psi.

 

[smokey]

those specs are with the regulator. the pump alone it can produce up to 60PSI IIRC

 

[Truckin4life]

Is he not getting enough fuel or is he getting to much?
I thought carb motors only need like 7 or 8 psi to run....

 

[smokey]

yep they need 6-8 psi.

 

[eco]

Guys, he is talking about the in tank pump.

These rigs have an in tank pump and a high pressure pump on the frame rail.

The in tank pump makes much less pressure than the high pressure pump. After the high pressure pump and after the regulator th PSI should be 35-45 psi. After the high pressure pump and before the regulator the PSI should be higher than 45, but not that much higher. After the in tank pump and before the high pressure pump.....well I don't know what that would be; I have never measured there. Not very high though.

I imagine that it would be viable to use the in tank pump, dump the HP pump and come up with a different regulator on a carb'd rig. I have never done it though or heard of anyone doing it.

 

[Bloodhound]

I will be home next weekend so I will have a chance to look at it. He got the truck for $500. He is always finding theese deals. So if he needs to put a little money in it it won't kill him.

 

[conanski]

The frame rail pumps ended in '89, so this '90 should have high pressure in-tank pumps only.

 

[Truckin4life]

Conaskit beat me two it....
There are only 2 pumps, one for the front tank and one for the rear tank, none on the frame rails...

 

[subford]

I was wondering if the in tank pump alone would have enough pressure to run a carb motor?

The fuel pump in a 1990 F150 is able to putout at about 95 PSI against a blocked head.
The fuel pump is rated at 125 LPH @ 310 KPA.
OR
125 LPH = 33.03 GPH
310 KPA = 44.96 PSI

This is too much for a carburetor and you will have to use an in-tank fuel pump from the 1986-1989 FI or carburetor truck. They put out about 5 PSI against a blocked head. Do not use the frame rail mounted pump off of one of these trucks.
The 1986-1989 in-tank fuel pump may not fit right in the hole of the 1990 as I have never tried to put one in one, you may have to get a 1986-1989 tank also.

If you still want to use the 1990 truck then you would have to put an adjustable fuel pressure regulator on it and adjust it to about 4-5 PSI.

 

[Bloodhound]

looks like that is the way he will have to go.

 

[bowtiehatr]

those ealy style pumps were notorious about pressure issues espeacially if it is a dual tank which im sure it is. if the check valves in the pump(s) have failed, i have seen low fuel pressure due to this and can see it causing a problem with the carb.

if the check valves are ok, the switching valve could be the problem. i have seen them where the valve sticks inbetween the two tank ports in the switch and cause the fuel to get bubbly or even a restriction.

 

[subford]

those ealy style pumps were notorious about pressure issues espeacially if it is a dual tank which im sure it is. if the check valves in the pump(s) have failed, i have seen low fuel pressure due to this and can see it causing a problem with the carb.

There is not a check valve in the in-tank pumps in the 1985-1989 trucks. The only check valve in the fuel system is in the frame mounted high pressure pump.
However the 1990 did have a check valve in its FDM but I think he said he only had one tank.

 

[bowtiehatr]

electric pumps have a check valve so they dont bleed back when you shut the truck/key off. i have checked to many for hard starts and replaced to many pumps for this issue. by the way, havent seen a 88-97 fi50 that didnt have 2 tanks.

 

[TexasNomad]

I all ways wondered why they all had two tanks..

 

[subford]

electric pumps have a check valve so they dont bleed back when you shut the truck/key off. i have checked to many for hard starts and replaced to many pumps for this issue. by the way, havent seen a 88-97 fi50 that didnt have 2 tanks.

It seems you do not know FORD fuel systems very well.
I just check two good fuel in-tank pumps that fit the 1985-1989 Ford Trucks and you can blow air back through both of them. I was sure they did not have check valves in them.
There are a lot of one tank Ford Trucks out there also.

 

[bowtiehatr]

i stand corrected on the older years. thank you for correcting me so politely. its the model year 90 and up that has the check valves i know for sure.

 

[Bloodhound]

Well I finaly laid eyes on my friends truck last night. It is a 89 F350 4x4, 351w, auto, with a welding bed on it. I didn't know that the F350's had a straight axle under them.

We eliminated the frame rail pump and the change over canister. Installed the electric fuel pump and the truck runs great. I looked close at what they did to eliminate the fuel injection. From what I can best tell all they done was install an intake and carb, used the factory dist with the prom removed. I know that it is still running the factory computer because the fuel pumps still came on like they were supose to. also I wired the new electric pump into the eec relay plug. I didn't know it was this easy to eliminate the fuel injection. I will keep a close eye on this truck and see how it works out. If he keeps it verry long. He only paid $500 for it. He has already been offered $1500.