Hey guys! I've been on here for a while but, right after I joined, I had some major changes in my life and haven't been able to really get on here. I just looked through 20 pages of search results on fuel issues and I'm not really finding anything that quite fits my problem but, maybe I'm not clicking with it.
First, a little history.
I have a 92 Nite with a 302 M5OD 2-wheel drive. The block cracked on the original motor so, I put in an autozone long-block. Rather, I had it put in as I was living in an apartment and had nowhere to work on it at the time.
Well, the idiots that put it in screwed-up all kinds of things! First, the block to ground wasn't connected at all and the negative to block was barely there which fried my stereo amp. The #8 plug wire wasn't even connected either! I'm amazed it ran to get it back to the shop!
After those problems were fixed, I learned the hard way they had routed some wires around the metal tube coming down from the EGR valve! One of the wires melted through and shorted out the fuel pump electronics. So, I have a dash mounted switch that grounds out the test connector in the EECIV unit so the pumps will run.
After that, it ran fine for quite a while. Then, suddenly it started starving for fuel under load. Idles fine, starts fine but, will not take a load.
As I recall, when I tested the fuel pressure at prime and idle, it was within spec. I did not get to test it while driving.
At the time, I just did not have the time to work on it so, I parked it and bought a full-size Bronco. (Love my Fords)
Since it had two full tanks, I used it as a super-tanker for my motorcycle. I connected a length of clear tubing to the fuel filter and flipped the switch on the dash and filled up the bike!
Now, here's the odd thing. When using the rear tank, there were lots of bubbles as in 3-4" long air pockets followed by about that much fuel in the tubing. The front tank pumped mostly clear but, would bubble a bit after a few minutes of flow.
I've read of a fuel pump on the frame rail but, I can't remember seeing one and haven't been able to get out to check lately.
I'm sure it's probably a mostly simple fix although it might require dropping the tank or raising the bed and I'm trying to decide whether or not to fix it or sell it as is. I don't have a garage to work on it. It's in the yard and that's where I would have to do all the repairs and it might have to sit for several days between each step.
So, my questions are: Does the collective genius of this site have an idea what the problem might be? (Side-note, I never had any signs of fuel flowing from one tank to the other. They allways emptied normally.) The other question would be: If you do have an idea, how difficult and costly do you think it would be? I really love the truck but, I'm just not up to lots of lying in the dirt under trucks anymore and it might be worth it to me to just sell it so I don't have to deal with it.
I thank the collective in advance for any help you may provide!

 

Does bubble quantity depend on fuel level in your really good-looking tanker? Generally there's no way for air to get into system, only if the pump is overheating, however, I never met this issue on any vehicle with electrical fuel pump (yet?). Pics of your clear tubing connection point may be helpful. My first and obvious guess is that something's wrong with pumps or fuel sending assemblies, but it looks too obvious to be true, you know... Just want to exclude other options.

 

Sounds like its sending pleanty of fuel to the filter...he's filling up his bike no problems

 

it does, but there should be no air as he's doing it.

 

It still had several gallons in it when it was bubbling. It was more air than fuel. The front tank had much more fuel and pumped better but, still had some small bubbles.
The tube isn't connected anymore but, when it was, I just had it connected to the end of the fuel filter on the frame rail under the driver door.

 

Nice looking truck

FH is right it should be a steady flow of fuel from the pumps with no air pockets. It could be you have somthing loose in the tank causing it to get air or it also damaged the pumps when the wires shorted out and its showing up now. Or it could be where you have the hose hooked up to the filter letting it get air there.

I would hook everything back up and do another pressure check on the system, also I fixed a pressure gauge where I can check the pressure while driving. While your at it also check the fuel regulator and the vacuum going to it as that's what regulates the fuel depending the load on the engine.

Cost wise depends on if you replace just the regulator,the pump or the whole assembly. Pumps run around $140+, whole assemblies around $200+ depending on brand name, regulators are about $25.

On a 92 there will not be a pump on the rail only the two high pressure ones in the tanks. The fuel going from one tank to the other is the check valves in the pumps getting stuck open or going bad.

 

Okay, I didn't think there was a pump on the rail on mine. I'll check the fuel pressure again and the vacuum connection you mentioned when I go on my 7 days off in a couple of weeks. I really don't like tearing into it unless I have several days to work on it since nothing ever really goes as planned! Thanks for the info!!

 

Bubbles in fuel rail 4.9L 1987 F150

Greetings, all. I have a problem I need some help identifying on my 1987 4.9L automatic F150 w/dual fuel tanks.

I haven't seen all that much discussion on the forums concerning this and have searched google but I am seeking vehicle specific advice if I can find it.

When I got this truck maybe one month ago it ran very well but several items needed fixin' and I've replaced the usual stuff...u-joints, wires, plugs, dist cap, rotor cap, ignition coil, TFI, IAC, O2 sensor, vacuum modulator, air filter, oil and filter, seafoamed the intake and fuel tank (one of them), blocked the egr valve (reversible), trans fluid/strainer, diff lube....etc etc. I haven't been testing these items, just 'throwing money at it'. I've got a coolant temp sensor and TPS left to change but likely won't get that done today due to incoming thunderstorms. I don't see problems I can't handle if I need to change the FRP fuel pressure regulator. I have a code reader but can't seem to get it to communicate with the 'puter on the truck. I believe that the plug on the truck is so crudded up (the cap was left off of it in the past) it doesn't make contact long enough to scan and report.

I started replacing parts when it would run rough after warm-up. Classic surging and faltering and racing and dying...mimicked a vacuum leak. Any number of things could be the root cause of the symptoms (thanks to the forums for educating/helping me on these things) and I would think I had it cleared up when it would return either quickly or after 2-3 days.

Yesterday I bought an 'Innova Equus' fuel pressure test kit which seems to be a fair enough quality unit for my non-professional needs. The fuel pressure was 58# I think...should have written it down. The fuel pressure did rise when I disconnected vacuum from the regulator and rose when I gassed the motor. It stayed steady and did not bleed off quickly when the engine was shut down. I noticed small bubbles in the clear bleed-off line when I was using it on the front tank....got to thinking about that and did a general google search and found some info on other makes of vehicles. I switched to the rear tank and hooked up the hose to the rail again but it was after dark, the fitting was leaking gas onto the convertor (yikes), and HUGE bubbles were coming out of the purge line.

My question is where could I be getting bubbles in the fuel lines? I can't think of anywhere there could be a vacuum pulled on the system except maybe between the in-tank pumps and the high pressure pump...possibly the tank selector valve or the filter or pump fittings.

One point I wish to make is that it appears that the fuel cap vent on my front tank may have been plugged as I noticed really high pressure on the tank 5-6 times when fueling...I didn't think that much about it but could that have caused problems with my fuel system? (The tank passed a pretty good pressure test without leaks due to this..lol)

The truck runs GREAT when it runs great...I've just got some intermittent problem I need to find the cause of (It ain't fixin' what's broke that's hard...it's figurin' out what needs fixin' that's the diff'culty.)

Thanks for any input/replies on this subject and apologies for the long post but I wanted to provide background to the situation. I'll post what caused the problem and the repair when I find out what it is. Regards.

 

Unfortunately, I don't have any answers for you but, thought I would return to the thread since I started it.
Shortly after I posted, a friend made me an offer on my truck I couldn't refuse so, it's gone. The truck still has the issue but, not as bad. When it begins to stumble, he says he backs out of it a bit and it settles down. He recently put a new high-power ignition in it and that has helped a lot but, the problem is still there. He is thinking of putting new pumps in and if he does and we find out what the problem was, I'll post up the answer.

 

I've noticed too that when I gas on it a bit...just keeping up with traffic/merging type stuff that it does fine until then although I'm not sure if that's due to fuel starvation/bubbles/whatever or if it's something else concerning engine temp.

I'd appreciate any info you come up with and I'll post what I find out in return.