Add One-way valve to keep fuel at the carb? '86 Burb 454

[suburble]

Does anyone have an exploded view or disassembled pics of one of the mechanical fuel pumps from a square? I'd really like to see how the pressure relief / return line setup is done.

Thanks,
-Josh

 

[HotRodPC]

Ok, so did you say you replaced all our fuel lines and you KNOW there is no air leaks? Then I'd go with this electric fuel pump and see what you get. The $23 is worth it for your sanity. https://www.amazon.com/CarBole-Elec..._3?s=automotive&ie=UTF8&qid=1496974799&sr=1-3

When I suggested Coil/ICM, it was after I read the other guy's post.

 

[HotRodPC]

Reason I'm suggesting this E Pump, is for diagnosis purposes. And then you can leave the pump in for emergencies in the future. Just unwire it, or put it on a toggle switch. If you put this pump in and you still have problems, then you problem is other than fuel pump related. It could be your pick up socks in the tank or tanks are gummed up, switching valve if you have dual tanks. If you're 100% certain it's fuel problem, and you've gone through all this, I'm going to say your fuel problem is behind the fuel pump.


In fact, if you can get a length of fuel hose and it doesn't have to fuel hose for a temporary run test, even clear tubing will work, get you a gas can, attach the tubing to in on the fuel pump and put the tube in a can of gas on your floor board and go for a drive. If it runs well, you're problem is behind the fuel pump.

 

[Georgeb]

For what it's worth I ran clear filters on three different trucks
Over the span of 20 years. Each one would regularly be mostly full of air or evaporated fuel when viewed at idle. I am also of the opinion it may be coil related rather than fuel related.

 

[SkinnyG]

I chased a fuel starvation problem for the longest time.

New Carter mechanical fuel pump when I put the motor in 3 years ago. Also two new tanks, two new pickups, and all rubber lines replaced. Within the first two years, it would run out of fuel during a full throttle run, usually half-way through second gear. Often while passing a car at the worst possible time.

Figured it was probably the pump - bought another NEW Carter mechanical pump. Absolutely ZERO improvement, right from the get-go. I figured it must not be the pump!?

Problem developed into fuel starvation on hot days. Usually stalling after a hot restart - usually within a block or less.

The developed into fuel starvation cruising on the highway when hot. Then only when warm. Then starving sitting in traffic. In all cases, plastic fuel filter was empty. In fact, rarely did I ever see the filter full of fuel at any time.

Removed the mechancial and mounted an AC/Delco EP12S electric pump at the back, nearest the tanks, at the lowest part of the frame. Problem gone. Like: GONE.

Went back to the mechanical pump, problem was right back again. Put the EP12S back in, problem gone. Lots of fuel all the way up through third gear wide open throttle.

 

[HotRodPC]

I chased a fuel starvation problem for the longest time.

New Carter mechanical fuel pump when I put the motor in 3 years ago. Also two new tanks, two new pickups, and all rubber lines replaced. Within the first two years, it would run out of fuel during a full throttle run, usually half-way through second gear. Often while passing a car at the worst possible time.

Figured it was probably the pump - bought another NEW Carter mechanical pump. Absolutely ZERO improvement, right from the get-go. I figured it must not be the pump!?

Problem developed into fuel starvation on hot days. Usually stalling after a hot restart - usually within a block or less.

The developed into fuel starvation cruising on the highway when hot. Then only when warm. Then starving sitting in traffic. In all cases, plastic fuel filter was empty. In fact, rarely did I ever see the filter full of fuel at any time.

Removed the mechancial and mounted an AC/Delco EP12S electric pump at the back, nearest the tanks, at the lowest part of the frame. Problem gone. Like: GONE.

Went back to the mechanical pump, problem was right back again. Put the EP12S back in, problem gone. Lots of fuel all the way up through third gear wide open throttle.

Moral of the story... You most likely had a worn fuel pump cam lobe and wasn't getting a full stroke on the mechanical fuel pump. An electric fuel pump is going to either solve his problem which I suspect it probably will, or it's going to tell him the problem is in the tanks, switch valve or fuel lines. BTW, If you do follow the advice of an E pump, do mount it as close to that fuel switch valve as possible. E pumps are more designed to push fuel instead of pull fuel so always get it as close to the tanks as possible.

 

[1987 GMC Jimmy]

I like the idea of the electric pump for diagnostic purposes. If possible, I like the mechanical setup to work on the carbed motors, but sometimes you gotta do what ya gotta do.

You've inquired several times about the one way check valve. I don't think it'll hurt if it's purpose made for fuel, and I think it's a very clever solution to have postulated given your take on the problem. I don't know if it'll offer any meaningful solution given the brainstorming that's been offered on this thread, but I don't think it'd hurt anything if you wanted to put one in there.

 

[HotRodPC]

I like the idea of the electric pump for diagnostic purposes. If possible, I like the mechanical setup to work on the carbed motors, but sometimes you gotta do what ya gotta do.

You've inquired several times about the one way check valve. I don't think it'll hurt if it's purpose made for fuel, and I think it's a very clever solution to have postulated given your take on the problem. I don't know if it'll offer any meaningful solution given the brainstorming that's been offered on this thread, but I don't think it'd hurt anything if you wanted to put one in there.

NO worries, one way or the other we'll get both guys fixed. I'm still not ruling out Coil or ICM for Kenny, and it sounds like Josh has confirmed with spray in the carb his is fuel related, but I said it early on, cam lobe or fuel pump not getting a full stroke to the pump. If it's not that, then it's behind the pump. The E pump will tell us that and he can leave it in as an aux pump on a switch if he solves the fuel problem and it's not the cam lobe. If it's the lobe, it's not worthy of a new cam if all the valves are working right, so keep it electric until it's time for a cam swap.

Also, this issue of a check valve is a moot issue in this case. This is a running and driveability problem. The check valve has nothing to do with performance. Check valve is for nothing more than quicker starts after sitting awhile, that's it and nothing else. My check valve in my 454 has been out since the day I got the truck many years ago. So what, I gotta crank it a little longer after it sits for more than about 16 hours, and that's also cuz the well plugs in my Qjet leak. I know this, and I deal with this, it's not big deal. Check valve for sure isn't the problem here and isn't going to fix a thing.

 

[suburble]

NO worries, one way or the other we'll get both guys fixed. I'm still not ruling out Coil or ICM for Kenny, and it sounds like Josh has confirmed with spray in the carb his is fuel related, but I said it early on, cam lobe or fuel pump not getting a full stroke to the pump. If it's not that, then it's behind the pump. The E pump will tell us that and he can leave it in as an aux pump on a switch if he solves the fuel problem and it's not the cam lobe. If it's the lobe, it's not worthy of a new cam if all the valves are working right, so keep it electric until it's time for a cam swap.

Also, this issue of a check valve is a moot issue in this case. This is a running and driveability problem. The check valve has nothing to do with performance. Check valve is for nothing more than quicker starts after sitting awhile, that's it and nothing else. My check valve in my 454 has been out since the day I got the truck many years ago. So what, I gotta crank it a little longer after it sits for more than about 16 hours, and that's also cuz the well plugs in my Qjet leak. I know this, and I deal with this, it's not big deal. Check valve for sure isn't the problem here and isn't going to fix a thing.

Yup. My thinking was I should be able to tell pretty quick if it's a drain-back issue if I put in a check valve.

I've got a cheap 0-15psi pressure regulator valve, too- If it does look to be a drain-back issue (due to bad pressure relief at the pump) I'm thinking of throwing that on the RETURN line from the fuel pump and seeing if that solves it.

Good thought on previous posts about problems between the tank and the pump. I can't totally rule it out, but I dropped the tank and replaced the sender and ALL soft lines between tank and pump, and the fuel fill and vent lines, and I think I caught all the emission lines, when I did the fuel pump last time less than a year ago.

Also, I suppose I can't completely rule out spark issues- WEAK spark could still see improved running with sprayed fuel. Ugh.

I'm thinking the cam lobe is probably good or it would be consistently having fuel supply issues regardless of temperature.

I still mentally loop back to "I shouldn't be seeing NO fuel flow at the filter" though.

Thanks,
-Josh

 

[donnieray]

Thanks suburble for starting this thread, and thanks to the helpful forum members for all the advice, I bought an electric pump Saturday and started with the C10 since its my daily driver. First I pumped straight from a can through the filter into the carb. The filter filled up, stayed full and held a steady 7psi. I then temped it to the feed line from the tank and got very erratic pressure basically the same conditions as the mechanical pump, conclusion, the damn metal line must be partially clogged with something that's able to move around a bit. I had replaced all the rubber lines but never thought about the metal lines. I disconnected the line where it turns toward the tank under the rear of the cab and blowed it out from the front with air pressure. Something came out of the line but who knows where it went. Then I removed the gas cap and blowed the short section out. Ill know by the end of the week but for now the filter is full, steady pressure and all seems well. Ill leave the epump in the truck but be using the mechanical pump. I also blowed out the same lines on my K10. Again, thank you guys. Suburble, you might want to blow your lines out sir. Ill update after a week of driving to work.

 

[SkinnyG]

I figured my steel lines were clogged, so when I went electric I also went through the lines I was going to use for EFI.

When I took all the EFI out (another story), I blew compressed air through the old lines, but they seemed pretty clear, so I am now running the electric pump through the old lines again. No problems.

I'm with subruble re:camshaft-pump-lobe on mine - I don't think the lobe went flat; I still had great fuel and power ~most~ of the time, but it would die off especially when hot underhood.

I also am running a pretty aggressive flat-tappet cam and valve springs, use Rotella oil and a ZDDP additive at every oil change, and have had oil tested by Blackstone Labs. No other lobes have gone, and if any lobe would go, it's not likely the fuel pump one. Having said all that, I ain't checking, because by golly, I'm quite happy with the electric pump for now.

 

[suburble]

Thanks suburble for starting this thread, and thanks to the helpful forum members for all the advice, I bought an electric pump Saturday and started with the C10 since its my daily driver. First I pumped straight from a can through the filter into the carb. The filter filled up, stayed full and held a steady 7psi. I then temped it to the feed line from the tank and got very erratic pressure basically the same conditions as the mechanical pump, conclusion, the damn metal line must be partially clogged with something that's able to move around a bit. I had replaced all the rubber lines but never thought about the metal lines. I disconnected the line where it turns toward the tank under the rear of the cab and blowed it out from the front with air pressure. Something came out of the line but who knows where it went. Then I removed the gas cap and blowed the short section out. Ill know by the end of the week but for now the filter is full, steady pressure and all seems well. Ill leave the epump in the truck but be using the mechanical pump. I also blowed out the same lines on my K10. Again, thank you guys. Suburble, you might want to blow your lines out sir. Ill update after a week of driving to work.

Sounds like a great easy check. I was planning on dropping the tank down a bit and checking all the line connections at the sender, I'll just pull them and blow a bunch of air through when I do it. As badly deteriorated as the old hoses were, I would not be surprised at all if there's a chunk or two of rubber bouncing around in there.

-Josh

 

[donnieray]

Exactly. I had lifted the bed on both trucks and replaced the pickup/strainer units and the rubber linesat the tank and also where they turn under the passenger side cab. Just never thought the metal lines may be clogged. I figure that any part you replace on a 35 year old truck is a good thing, especially rubber. Ive drove to both jobs today, one is a 7 mile cruise on I-95 and popped the hood with the engine still running when i got there and the filter is remaining full. Time will tell though. I have a third square that Im just getting to know that dont have this problem, but as soon as I get time Ill replace the rubber and blow the lines out.

 

[MikeB]

Welcome to the wonderful world of Edelbrock carbs. Your problem (hard to start after hot soak) is very common on hot days, and gasoline with 10% ethanol doesn't help. I ran a 1406 back in the mid-1990s and never had a problem. Same is true of the old AFB's which are very similar. But I started seeing the problem with the 14xx series carbs 10-15 years ago, especially during our hot Texas summers.

A fiber, wood, or phenolic spacer will help, but I'd try to use one that's 1/2" thick. Edelbrock makes one that's around 5/16", but it frankly doesn't do much good. Also, its surface may tear when you remove it.

I've always thought the fuel evaporated, but you bring up an interesting point about it running back into the fuel line. I wouldn't think fuel pumps would allow fuel to drain back through them, but who knows?

 

[SkinnyG]

Follow-up to the dubious fuel pump issue - I took my "failed" near-new fuel pump to school to show my students (I teach highschool mechanics). The plunger inside isn't going down - the lever to operate it moves, yes. But the plunger which should be pulled down by spring pressure is not moving. So - the pump has indeed failed.