intermittant fuel supply problem?

[todd.a.nance]

i have an intermittant problem with my 4x4 suburban. it seams that 'periodically' as i'm driving along that the fuel supply seems to cut out and then back on repeatedly until i have to pull over and restart the vehicle. once i pull over, the vehicle either idles just fine or sometimes stalls out.

i have had it in the shop last nov. and the mechanic said it was related to loose baffles in the fuel tank. problem seemed to be fixed then (baffles secured and new fuel pump added).

more recently i had it in the shop again after problem began recurring. now shop throws up it's hands and says they don't know what is wrong. since the problem is intermittant and they cannot seem to recreate it in their shop they say they can do nothing.

has anyone else had a similar problem (k5, sub, or other)? how did you fix it?

regards,

todd nance

 

[Can Can]

Give us a bit more info.......What year is your sub? What kind of fuel supply- mechanical pump on the block, or electric in the tank? If you have a mechanical pump, the diaphragm could be getting weak and will cause vapor locks.

 

[smack]

Also are you sure it's fuel related? And does it happen only when it gets hot?

 

[todd.a.nance]

1990 suburban 4x4. electrical fuel pump in tank and electronic fuel injection.

i don't have any experience with vapor lock. does it apply to fuel injection or just carburetion?

engine temp never seems to get too high. temp guage stays around 180-210 in terms of normal high temp range reached.

once problem exhibits itself, it will continue to recurr as i get back on the road and speed approaches 35-40 and beyond. best i can do is limp home. however, after sitting (10-20 minutes) i can drive it and it will not exhibit the problem again until some future time.

what else do you need to know?

regards,

todd nance

 

[todd.a.nance]

i'm not certain that it is fuel related. since the problem is identical to the 'loose baffle' fix (baffles supposedly periodically migrated toward fuel pump and interfered with fuel flow) my initial reaction was that it is fuel related. however, i am interested to hear if others have had a similar problem.

 

[Topher]

I had a similar problem as far as the symptoms being almost identical (intermittent, cuts in & out, 35-40mph, etc.). But it was on my '85 carbeurated Jimmy and was directly linked to a shot mech fuel pump (front pass side of block FYI). So I'm clueless as to whether the problem I had has any relation to a newer vehicle w/ EFI and an electric pump. Well I replaced the pump and the problems went away immediately. BTW I took a look inside the damaged unit and was surprised it was even working at all! For awhile I thought it was my carb acting up or an extremely clogged fuel filter but I figured I'd start from one end and troubleshoot to the other. Turns out it was indeed the pump.

But like I said almost all the symptoms described above are identical to mine. It basically sounds like fuel starvation of some kind to me; but due to what and where I don't know unfortunately. Wish I could be of more help.

Chris Southerland
DFW, TX
85 Jimmy & 78 K5

 

[Blazer79]

I had a very similar problem on my Blazer, only mine is a 79 with mechanical fuel pump on the engine block and a Q-jet carburetor.

If the misses are really short, it could be an ignition problem. Check out your spark plugs & wires, distributor cap & rotor and module.

However, if the misses are a bit longer, (as if someone was playing with your ignition switch) it could be fuel-pump related. That's what happened on mine. City driving and short trips were no problem, but on long trips, once it heated up, it started to miss this way

First I didn't know where to start. I changed carburetor because it gave me a hard time in cold mornings anyway, the missing problem remained. Then I changed the distributor. That got rid of the high-rpm misses. Then spark plugs & wires, but the longer misses were still there.

Just this past weekend I replaced the fuel pump with a new Holley performance one. According to the other guys in this forum, it was definitely vapor-lock. I also added a fuel pressure regulator and a fuel gauge, just to make sure everything is fine.

Tomorrow I'm making my first long trip. I'll let you know how it goes.

Have you ever replaced your fuel pump? You should follow your gas lines, maybe a bracket or something came off and the fuel line is just too close to the exhauxst.

Good luck. If you have more questions, don't be afraid to ask.

<font color=black>//////
What the heck!...Drive it like gas is $0.50/gal!!!</font color=black>

 

[Bruiser]

What about the fuel filter? Have you checked it and or replaced it? I used to have this problem on and 86 cavalier I had, would run fine then just start cutting out, roll over to side of road or limp there, sit few minutes it would then run fine.


Vincent Michels
1978 Blazer
Bruiser (Frost white/Black top/ Light Blue interior)

 

[Eagle86K5]

Same thing happened to me with the old Northern Telecom company car, Chevy Citation, it was the fuel pump. They practically replaced the whole car till one guy dropped the tank and replaced the pump, it ran great after that.

<font color=green>

Eagle86K5

<font color=red>
Masonry...It's a Good Thing
2B1ASK1

 

[DMK]

Buddy of mine had an s-10 blazer doing the same thing and a mechanic told him the baffle story. Turned out the distributer was bad, replaced the distributer no more problems. The truck was a 91.

 

[KrebsATM02]

Hey mine ran like you are talking about, but all the time after it happened. Basically the enigine loped and if you gave it much gas it didn't sound healthy at all. One of my slip nut/washer things came loose off the stud that holds the baffle on and let the baffle swing in the gas tank front to back. After enough off roading i guess it finally jarred it hard enough and it hit my fuel pump pretty hard and caused the pump to come off a little from the 1.5 inch black fuel hose between the sending unit and the pump. The result was not addequate fuel pressure and the pressure regulator was trying to compensate but it couldn't. I found this out after rebuilding the tbi, map sensor, tpr, and all the other stuff in there. Let me know if you have any questions. Hope this helps - Doug

 

[getsome]

I had the same problem on my 84 K5. Kind of like a hellish miss but it would idle fine when I pulled over. I replaced the fuel pump and it was fine for about a week then it started again. I mounted a electric fuel pump by the tank and ran it through the same line to the stock pump and nothing changed so I bought 15 feet of 3/8" hose and ran it strait to the carb. Problem fixed. Did I get a bad pump? Have no idea but I can tell you that the electric pump works great and the problem is gone. Don't know if this helps or not but don't you feel better knowing that your not alone?

Getsome

 

[coopertwpk]

I have had this happen on my 91TBI s10 and my 88 v10TBI blazer it was the pickup in the distributor.took forever to figure it out.