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**Update ** to my random shut down issue –

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K5_Fla

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84 K5 – newer TBI motor converted to Edlebrock carb – electric fuel pump in the tank.

I have been fighting a problem with the truck randomly shutting down – like it’s running out of gas. Did a ton of things already, nothing helped. But I think I’m getting close.

My first questions - should the fuel pressure remain constant at ALL times even at idle? I was watching the pressure gauge at idle today and the pressure dropped from 5 psi to 0…. Sure enough the truck would blog and then stall shortly after this happened. That has to be the issue here.

It did this a few times while I watching it…

So it seems my issue is the fuel pump, fuel regulator or fuel rely. By the way.. all of these parts have been replaced in the last year already. Fuel filter was replaced last week when all of this started.

I can change the fuel rely and regulator pretty easy… but don’t want to mess with the fuel pump unless I have to. Any way to tell what part of the fuel system would be the issue?
 
I would think its the pump.

Where did you get the replacement pump? Ive had nothing but bad luck with parts store TBI pumps in the past.
 
Carburetors can handle an occasional loss of pressure, since they have a fuel bowl they draw from.
Fuel injector systems are just the opposite. They must have available fuel at all times.

That is the main reason for the return line and pressure regulator. Not only does the fuel rail have to have constant pressure, it has to have instantaneous flow.
When the injector opens, there is only a few milliseconds for the gas to get into the intake.
So the system supplies more flow and pressure than the engine needs, and the regulator dumps the excess back to the tank.

But, even a carb has its limits. Sounds like the fuel flow is staying off longer than the fuel bowl can cover.

In your case its almost certainly the pump. Its unlikely that the filter would stop up and then open back up.
And the regulator might malfunction and dump all the gas back to the tank, but I would expect it to be able to stumble along.

Having written that, something occurs to me. How does the pressure regulator on your setup work?
FI engines dump the excess pressure and flow back to the tank. But in your case, it might just restrict the pressure down to what the float valve can handle.

I have seen both types. Bypass and restriction.

Remember the FI setup used the computer, and the oil pressure switch to turn the fuel pump on.
Since yours is a conversion, how much of the pump control system is still used?
If its cutting off at idle, your oil pressure might be dropping to the point that it kills the pump.

You might try rigging a temporary power lead direct to the pump, controlled by a switch on the dash, long enough to see if the problems goes away.
 
With some FI regulators, you have a vacuum port that varies the pressure according to throttle opening.
When the vacuum drops due to a sudden opening of the throttle, it boosts the pressure so that the injectors put out more gas per millisecond.
Acts like a accelerator pump on a carb.

Your regulator has no vacuum port, or any other way for the pressure to change automatically.
Which means you should be able to set it, and it will maintain the set pressure as long as the fuel pump puts out more than the setting.

So, unless you are running a huge engine that sucks more gas than your pump puts out.........
Not likely, especially at idle.:D

There is no reason for the pressure to drop below the setpoint.
So, either the pump is failing or the regulator is dumping all the gas.

Pumps can fail intermittently, but usually they either quit completely, or get weak.
I would suspect power problems to the pump first.
Easier to check than changing the pump.

If it turns out to be the pump, remember the option of cutting an access hole instead of dropping the tank.
 
ok fordum.. thanks. Pressure should be 5 psi at all times.....
 
I guess it wouldnt hurt to change the pump rely? it's cheap and fast... what do you think? I may do this and the regulator first..
 
I hate the thought of dropping the tank right now when it has 25 gallons of gas in it..
 
K5_Fla said:
I hate the thought of dropping the tank right now when it has 25 gallons of gas in it..
Click to expand...
That is why my mechanic friend has two prices for changing the pump in most vehicles. One for dropping the tank, and a cheaper one for cutting an access port in the bed.

And an even cheaper one if the port is already there.

He has gotten real good with cutting the hole and fabricating a door to go over it.

A couple of folks here have pulled the body instead of dropping the tank.

As for changing the relay and reg., its up to you.
Won't hurt anything but your wallet.

But I would consider running a switched hot wire to the relay to bypass the regular control to see if it cures it.
 
alright.. I guess I'm dropping the tank. managed to get all the gas out of the tank... looks like my sender is screwed up (under 1/2) tank anyway... does anyone know the best place to buy a AC delco pump and sender unit (31 gallon tank)
 
Um,maybe the carb should be looked at first in case a float is sinking or needle valve is sticking ,that will bleed off the fuel pressure quickly...then recover just as fast as the float rises again--Edelbrocks have a pair of floats,one could be filling wuth gas perhaps.. ...it could be cdud in the tank or water in the tank clotting against the sock filter,and that split peice of hose that so many here found after removing the pump...

I feel for ya,I hate electric "in tank" fuel pimps...worst place ever to hide the frigging fuel pimp,IMO..whoever invented that should burn in hell!.
 
thanks man... carb was just rebuilt as I thought it could be the issue you stated. Float's are floating , tested and set 7/16. New needles/seats/accelerator pump, the whole 9 yards.

I'm dropping the tank soon to start checking out things in there.
 
Ok, I dropped the tank and look what I found … not sure if this is my only issue… but it’s defiantly a issue. The fuel line is crimped so bad I don’t know how any fuel ever made it through.

Question is .. how do I change this… the braded part is clamped into the steel line. Is there an easy way to put a new braded piece here?

397986926.jpg


397986923.jpg


397986927.jpg
 
Which line is it? Fuel out, return, or vent?

That crimp is no big deal. I have literately done thousands in the beverage trade.
All you need is a hose, sleeve, and a crimping tool.
Trick is, finding them. You would have to find a piece of fuel rated hose like that, and I'm not sure where you would find it.
They sell braided fuel line at various places, but you will have to figure out what size you have.
Plus, a good quality hose clamp is just as good as a crimp.

PickandPull is going to be a good idea. I suspect that most of the lines are the same, so get as new a model as you can find to make sure the hoses are new.

You can cut out that section, put in a double barb fitting and either crimp the connections, or use good quality hose clamps.
 
that's the fuel out line... that has to be my issue with the truck randomly shutting off.... it starved for fuel sometimes. Anyway.. I'm going to fix that, get a brand new tank and sender pump just for hell of it. I want to fix it all and never have to drop the tank again.
 
Fordum.. also.. would be a totally bad idea to just use a rubber fuel line there? I could fix it in 1 min if that is the case...
 
K5_Fla said:
Fordum.. also.. would be a totally bad idea to just use a rubber fuel line there? I could fix it in 1 min if that is the case...
Click to expand...

Well, the pressure is not that high. The braid is for abrasion resistance and cut resistance not pressure.
Under that braid is a rubber line.

Given that we are working with gas, you definitely want the protection since it is downstream from the pump.
With the older engines, a hole in the gas line coming out of the tank would suck air.
A hole in this one sprays gas everywhere.

You can probably find what you need at a parts store.
I found this stuff online. Sounds good.

http://www.carpartswholesale.com/v5...Line/THE25080.html/?sc=Product+Listing+Page:1

The tricky part is going to be getting the old rubber hose off. You can cut it after the barb to get some working room, but the only way you are going to get the cut piece off, is by splitting the crimped sleeve.
Normally I use a Dremal tool with a cutoff disk and just slice it lengthways. But, its a steel sleeve, and you will get sparks. So maybe a file or a set of wire snips.

I understand about a new pump, but unless its really rusty or dented, a new tank seems like overkill........
 
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