guitarman2

Anyone use the jegs in-line fuel pump for carbs set at 6.5 psi? I installed one and it won't maintain pressure after it gets hot; I mean 0 pressure. The problem occurs when I stop for a minute and then resume driving. The motor runs til the carb bowl empties out then stalls until the recirc in the pump opens back up. I emailed jegs about it a week ago but no reply as usual. Any ideas?

Restrorob

iTrader: (7)

In my experience with in-line fuel pumps, Their not worth crap for a street application. I went through 3 different brands in 2 months on my truck (yes they were installed correctly), Install a stock TBI pump (lower pressure) in the tank then a regulator with return line back to the tank. Adjust to your 6-6.5 lbs pressure and call it a day.

My truck has been run'n flawless with this style set-up for 5+ years now......

RedLeader289

iTrader: (2)

Don't know if my situation is a rarity or what, but my Holley blue pump has been running strong for about 7 years now, no issues.

It sounds like your fuel is evaporating in the line. I used to have the same issue.

Take one or two wooden clothespins and clip them onto the fuel line in front of your regulator. This will either alleviate the problem or narrow it down and tell you that the fuel is not evaporating.

I've attached a pic for reference, you can see that I currently have 2 clipped onto my fuel line.

It sounds crazy, I know, but it works, has something to do with heat dissipation through the wood.

guitarman2

Thanks. I'll try that. I thought that might be the problem, but it didn't occur to me it could be the line before the pump.

five7kid

iTrader: (14)

I agree with everything you said except that the TBI pump is lower pressure. It is actually lower capability.

If you're putting in an in-tank pump, use a good one. A TBI < TPI < Walbro 255.

guitarman2

I'm skirting an in-tank pump right now, in fact I put an in-line glass filter before the pump as jegs suggested and that may be my problem. I tried the clothes pins and it didn't help, but I may not have had them in the right place since the lines are clamped to the frame. But I did notice that there didn't seem to be any fuel in the filter after I stopped. My question to jegs was: can I take the recirculation pin out of the pump and use an external regulator. I have a holley bypass type regulator I installed initially, but removed it as the recirc and the regulator seemed to be fighting each other. Now I see my problem may have been vapor lock all the time. The stalling problem was the same with either setup.

RedLeader289

iTrader: (2)

I could be wrong but you may have your pump mounted in the wrong location. Did you verify it was a "puller" pump? Because my in-line pump is a "pusher" pump and must be mounted as close to the tank as possible in order to function properly. That might be worth you looking in to if you haven't already.

Ozz1967

iTrader: (4)

I went through 3 Holley Blue Pumps, all mounted in the rear next to the tank. Burned them all out inside of 2 years when I did my motor swap (305-350, no mechanical fuel pump provision). I then tried a Holley Black pump, same issues. Now I'm running an In-tank electric, 255lph, walboro pump with adjustable return-style regulator to bring the pressure down to 5.5PSi. I've had zero issues in the past 4 years.

Breaking down and taking the day to pull the tank, install the pump, run the wiring and put everything back together was well worth it in my opinion.

guitarman2

Yeah, I'll probably end up putting a pump in the tank. Thanks for the input, guys.

Ozz1967

iTrader: (4)

You'll not regret it.

I think the main issue with these in-line pumps, is that when they stop running, the fuel goes back up the lines and into the tank, forcing them to run "dry" for a few seconds while pulling fuel from the tank. This causes mad heat and burns them out. The only way around this, I think, would be to put a sump in the bottom of the tank with lines to gravity feed the pump.

guitarman2

Because the tank is up behind the back seat I'm pretty sure I have a gravity feed situation. I just picked up a "T" to install after the pump and hook my recirc line back up. Hopefully the pump will maintain at least 3# pressure to the carb.

Restrorob

iTrader: (7)

Lower capability

Most GM TBI pumps are rated between 12 psi and 15 psi;

http://www.howstuffinmycarworks.com/..._pressure.html

Most GM TPI pumps are rated between 38 psi and 48 psi, #29 here;

http://www.classictrucks.com/tech/04...ion_questions/


My truck had a MPI 4.3 in it for the first 20 minutes of it's life (off the showroom floor) before the crate BB 502 was installed, The factory MPI pump is rated at 54 psi to 62 psi..... The early TBI tank and pump I installed is rated at 9 psi to 13 psi ......

The way I see all these specs, A TBI pump IS lower pressure than a TPI or MPI pump. I changed to the TBI pump in fear of burning up the higher pressure pump choking it down to 6 psi for the carb, And......My BB 502 has been running flawlessly over 5 years on this TBI pump......

guitarman2

Right. I didn't know the in-tank pumps were different pressures. I have contemplated going to the bolt-on tbi, but I see many factory fuel injection owners are switching back to carburetors on this site and in a mag I get called car craft. Anyway, the conversion tbi comes with a fuel pump I assume is the one with lower pressure. That option is cost prohibitive for me anyway at present. Thanks for the info.

guitarman2

update on my vapor lock situation. I installed the "T" after the pump and ran a line to the factory recirc, which I had capped off thinking I could rely on the bypass in the pump, and eliminated the vapor lock. Now there is constant flow back to the tank and my next dilemma may be will I shorten the life of the pump by constantly pumping back to the tank. The pressure to the carb still goes down to 0 on occasion, but now I can run as hard as I want with no stalling.

naf

iTrader: (7)

You must maintain the recirculation on the carb set up. The fuel lines are too close to the exhaust manifold. The lines will heat soak and the fuel will boil in them.

The pump should be fine running continuously, in fact, it's probably happier with a constant flow of cooler fuel running through it.

Your 87 should have an in-tank pump that assisted the mechanical pump. It isn't strong enough to feed the motor by itself though. I'd verify that it is still functional (you can jump out the fuel pump relay plug). If it's fubar your in-line pump will be fighting to pull fuel through the restriction that a dead in-tank pump becomes.

guitarman2

First I've heard of a booster for the mechanical pump, I'll check it out. I think the electric pump will be ok as well, as it may run cooler due to the recirc. It is the original
design after all.

five7kid

iTrader: (14)

Pressure is a function of resistance to flow. If there is no resistance to flow, there will be no pressure. On the other hand, block off the outlet to a TBI pump, and the pressure on the outlet will be much more than 15 psi.

"Capability", as I used the word, is a function of pressure and flow. Note that fuel pumps are rated for flow - unrestricted. To maintain that flow at pressure requires more "capability".

You can use a TPI pump in a TBI application because the fuel pressure regulator will maintain the outlet pressure at 12 psi - the excess "capability" will be returned to the tank. Ditto a pump like a Walbro 255 - it'll maintain the 43 psi a TPI engine requires, but will also work fine in a carb'd application at 6 psi with a return-type pressure regulator. But, a 255 will support more power in a carb'd application than an EFI application, because the lower pressure will allow it to supply more flow (and horsepower ultimately is a function of fuel flow to the engine - along with the proper proportion of air, of course).

guitarman2