fuel delivery question

[midnite]

first let me start off by saying hello to everyone here. i recently purchased a 79 ford f250 2wd with a 300 i6 and a np435 4spd transmission. now for my question. ok now i know that this may be a simple fix but would like to just have some verification before i go spending money on random parts that i think may be defective. last week i purchased a new fuel tank for my truck(the original one was rusted really bad. after purchasing and installing the new tank and draining the fuel from the old one(no point on wasting the 10 bucks i just put into it) and adding some extra for good measure on my way home my truck shuts off with no warning. no sputtering,jumping etc i manage to coast it into a vacant lot and try to restart it a few times. i figured that i didnt have as much gas as i thought i did so i grab my gas can,walk the 1/4 mile up the road purchase 2 gallons of gas(plenty to start it and drive it to the gas station) and pour it into the tank. my truck has an after market electric fuel pump on it so i turn the key on and let it "re-prime" the system. i let the pump run for 10 seconds to try to avoid flooding the carb. i then try to start it up and got nothing. i tried this for about 20 mins and it didnt start. so i pulled a plug outta the engine and disconnected the coil to distributor wire and attached the plug. cranked the engine and had spark from the coil so i re attached the coil wire and connected the plug wire to the plug and did the same and once again i had spark. this tells me i have a fuel delivery problem. i re-install the plug and wire and attempt to start the truck again with no luck. it only fired when remembered that pouring gas into the carb would gurantee fuel to the engine for a few seconds at best and it would atleast start. after 2 or 3 attempts using this method the truck started and ran fine that was last tuesday. ran the truck up until today with no problems what-so-ever. after leaving work today i get into my truck and start it up. it runs for 30 seconds and then does the same thing. it died with no warning. i try to restart it and again nothing. so i recheck my fuel lines to make sure they are free of kinks,breaks,leaks,etc. found nothing. called a family member who lives close by and they bring a can of gas and it would only start and run long enough to burn what i poured into the carb and then die again. so i check my fuel lines again this time disconnecting sections and turning the key and looking for free flowing fuel. during which time i notice that the fuel was being pumped and then would quit and then start again. i determined that there was a blockage in the line. i found and removed the blockage (rust build up from the original tank) the pump worked perfectly. on the drive home it decided to try to shut off on me again but would then catch itself and continue. the truck has been doin this all night and only does it when going up certain hills. i plan on replacing the fuel filter on tuesday when i get paid but im looking into other possibilities incase this doesnt fix the issue.also checked all wiring and grounds to the fuel pump to make sure they were secure and found no cracked or broken wire anywhere. so any insight as to the cause of and solution to this problem would be greatly appreciated. sorry for the length of the post but i try to be as in-depth as possible when explaining vehicle problems. thanks for the pointers,bill

 

[fatherdoug]

If you're getting intermittent flow out of the fuel pump, then the problem would be either pluggage on the suction OR discharge side of the pump or a failing electric fuel pump.

Do you have two gas tanks on the truck, or just one?

 

[G.O. Stang]

Sounds like some junk got to the pump. It's either clogged or going out. Check the fuel pressure. It's got to be around 3-7 psi. Any less and it won't be enough. Honestly, I would go back to the mechanical pump. It's a lot more reliable and less of a headache when issues arise. Plus it's much cheaper to replace if necessary. I know lots of guys who use mechanical pumps on their 500hp NA motors, so they aren't junk by any means.

But back to your current issue, again, check fuel pressure at the carb and report back. Also probably wouldn't hurt to disconnect, inspect, and clean out the fuel lines. How did the pickup tube look when you replaced the tank?

 

[midnite]

to answer both questions. i only have one fuel tank(although i think the truck originally had 2) i have a selector switch on the dash but no 2nd tank. the only tank i have is located behind the rear axle. and the pick up tube and sending unit looked decent when i pulled it out of the tank. no dirt or debris in the tube or in or on the screen. i know that my truck is a fixer upper and thats what i was looking for. an inexpensive drivable project vehicle. i paid 400 for the truck and it runs great aside from the busted leaf spring and fuel flow problem. but a new mechanical pump is on my list of replacement parts come payday. but i will definately keep you posted on the fixes and updates. i do know some about vehicles and i learn as i go so ill try and help everyone on here as best as i can. also if you have anymore tips,pointers,or advicefeel free to let me know, i always welcome any help and its always appreciated. thanks for the advice its greatly appreciated. thanks again bill

 

[m78]

Just a thought, did you check for fuel vapor lock ? Does the gas line run to close to the manifolds or block ?

 

[DNFXDLI]

Also, isn't there a small piece of rubber line off the tank that is prone to cracking and sucking in air?

 

[G.O. Stang]

Any rubber line is prone to that I think. Anything rubber before the electric pump could potentially be an issue so it doesn't hurt to replace them.

 

[midnite]

i know what vapor lock is. but i dont kno0w how to check for it lol. i thought the engine had to be warmed up for vapor lock to take effect. in my case the truck sat for about 5 hours when this issue occurred. as for the fuel runninhg in close proximity to the block etc yes it does. it runs through a steel line until it reaches the engine compartment then runs through a rubber line for about a foot or so then back into a steel line up until about 3 inches from the carb the back into a rubber line and into the fuel filter and into the carb.(whoever installed the electric pump used the original fuel lines and jus simply linked them together and made it work that way instead of doing it the proper way i believe) as for a rubber hose from the tank to the pump yes there is one there and when i replaced the tank i noticed it was starting to crack so its been added to my list of parts. however i put 30 dollars worth of gas in my truck tonight (about 1/2 tank worth) and drove around for about an hr and a 1/2 and then came home and had no issue what-so-ever with the truck wanting to stall while goin uphills. so maybe the pump was sucking air from the tank when i hit a hill due to the fuel sloshing to the rear of the tank?? either way im still going to replace the pump to be safe as well as the rubber hoses and filter(s)

 

[chris989]

Dump the electric pump

X2 on going back to a mechanical pump. Electric pumps push better than they pull. And when they get hot, they vapoolock. That is one of the reasons they are inside the tanks in newer cars.

My 75 Trans Am with a stewart warner electric would always vapoolock. The pump was to near the heat of the exhaust. I went back to mechanical. The car ran 13.50s all day capped with street tires. The mechanical never let me down.
Chris

 

[midnite]

update; i got a new mechanical pump today and installed it and replaced all of the rubber lines. the truck now runs great. after installing the new pump i went ahead and cranked it to "prime" the system and to my surprise the truck fired right up after only about 5 seconds of cranking and stayed running with no problems and so far its working perfectly. then i noticed when i got home that the tranny was very difficult to get into reverse and thought my clutch was goin and startd looking at the tranny and noticed that they can be adjusted so i did just that and adjusted the clutch and now no problems there anymore also pulled the carb and hosed it down with carb and choke cleaner. when i pulled the carb i noticed the rubber hose from the pcv valve was connected to a vacuum line on the carb :s i dont know who thought that was a good idea but the carb was loaded with oil but thats been fixed too. now for the rear brakes but ill put that in its own post here in a few.

 

[fatherdoug]

Glad to hear things improved. The PCV valve line is supposed to go the back of the carb. That is the vacuum source that keeps the valve open. If you're getting lots of oil into the carb, then you have other issues.

 

[m78]

^ a little blow by the rings ?

 

[G.O. Stang]

Depending on the age of the engine, some old oil is normal with a PVC system. Just clean it out, replace the PVC valve, and go down the road. Check in a few months and if its back as bad as it was, then there is another issue.

Alternatively, you can install a catch can to better monitor how much oil is coming through the PVC.

 

[m78]

Years ago I had a I6 in a pickup. The thing would spew a mix of moisture and oil mix in the form of milk shake. I never had a problem other than that, so I just put a piece of tubing down from the PCV and let it drip.

 

[fatherdoug]

Years ago I had a I6 in a pickup. The thing would spew a mix of moisture and oil mix in the form of milk shake. I never had a problem other than that, so I just put a piece of tubing down from the PCV and let it drip.

Guess that's why they used to call them blowby tubes, before Congress developed a conscious.

 

[chris989]

oil consumption

I had a 390 in an old ford and it used a ton of oil. Come to find out the oil passages in the heads that allowed the oil to return to the pan were severely blocked with crud. The oil was trapped on top of the head and would seep in pass the valves.

Once the ports were cleaned,, no more oil burn.

Just a thought,
Chris

 

[midnite]

the pcv valve hose was connected to a piece of metal line (vacuum choke) maybe? i removed the line and plugged it with my finger and the engine running and it didnt do anything just stayed running same speed and all so i went ahead and plugged it. i didnt see a connection on the back of the carb to hooke the pcv valve to and the line im talking about if your standing in front of the truck looking at the carb it would be on the side next to the valve cover

 

[dustybumpers]

You need the pcv to work. If you don't want to have it hooked to the carb, at least hook it to the intake manifold.

I would probably do a compression check to see what's going on. I imagine you have worn or broken rings with that muck blow by.

 

[G.O. Stang]

You need the pcv to work. If you don't want to have it hooked to the carb, at least hook it to the intake manifold.

I would probably do a compression check to see what's going on. I imagine you have worn or broken rings with that muck blow by.

You don't NEED a PCV. That's why they sell breathers. However a PCV system is ideal for a street vehicle.

 

[midnite]

i know what pcv stands for positive crankcase ventilation and the it supposed to help "release" the built up gasses from the engine but other than that what else if anything does it really do?