Intermittent stalling

Johan

Supporter
Whew…. OK. The fuel pumps, swirl pot and filters are effectively insulated from heat. Vapor lock is usually a situation where the fuel is being drawn over a long distance ie rear tank~front engine/ fuel pump. It usually doesn’t happen with elec pumps located at or in the fuel tank. This is a loop style system where the regulator returns to the swirl pot. Mike I’m at the point where I need to retorque everything. You are correct the LS is susceptible to intake leaks. In my experience that shouldn’t affect the driveability under loads. I have some more things to check as well. Johan that is basically the system I’m using , just also using a low pressure pump to fill the swirl pot. I’m suspicious the low pressure pump might be not supplying enough to the swirl pot. Back to the drawing board. Hey Neil because this system is a looped system the high pressure pump over provides fuel which normally returns the unused amount to the swirl pot. As far as stressing the high pressure pump under a load wouldn’t the pump be effectively under less stress because it supplies the same volume but less is restricted by the regulator as more is used by the engine. What effect on its load/ draw be?
Thinking of what Mike said, couple of years ago I had a problem when decelerating with closed throttle (engine braking) and when I pushed the clutch the engine sometime died. Ended up re-mapping with Alpa-N in the idle area. A while later I had the intake off for another reason and installed new gaskets and the problem was gone. So most likely intake leak.
 

Rich Kruger

Supporter
I don’t discount any of these theories. I’ll be busy this weekend. As far a reprogramming I wanted this resolved before I get it dynoed. It is a steady throttle/accel situation and it definitely affects the high pressure pump.
 

Rich Kruger

Supporter
After testing a few things a roadrest revealed the swirl tank was running dry. The low pressure pump was screaming hot when it stalled. Research on the Holley HP125 shows a lot of people have had this concern. ASAP I’ll disassemble it to see if the brushes are disintegrated like other users have posted pictures of.
 

Howard Jones

Supporter
Here is a wire gauge to current chart. You can see that you can be marginal at 10 amps depending on wire type. I like to overrate by 33%, and in this case, be good at 15 amps continuous. Try adding a second temporary wire to the power circuit effectively doubling the wire size for the test. If that's not it inspect the connectors and be sure that the crimps on the lugs/pins are good and tight. Use the correct crimping tool if you can. I crimp and then solder my critical circuit connectors.



HP125: All of these types of pumps MUST have the input port continuously below the fuel level. They will not lift fuel. I went thru a similar discovery process with a Holley pump that is of a similar design. You have plenty of volume but I bet it is not picking up fuel as the "head' gets near zero, gets hot each time it runs dry, and then draws some more fuel intermittently.

I switched to one of these:


It will lift fuel at least 18 inches. That's what it is doing in my SLC.
 

Rich Kruger

Supporter
Disassembled the Holley HP125 and found the brushes disintegrating and the commutator badly scored. There were pictures very similar on Summit .com with the stories. The pump is mounted two inches above the bottom of the tank. I’ve never needed more than 7.5 gallons when getting fuel so I don’t believe it was a lift concern.
 

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Randy V

Moderator-Admin
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Lifetime Supporter
I think I’d be contacting Holley about that pump failure. There may have been trash left inside the pump‘s brush cavity during assembly. These pumps should be capable of a thousand hours of use without failure. This type of issue may also be indicative of why fuel pumps were moved into the fuel tank and have the fuel itself flowing through the brush cavity to keep things cool.
 

Neil

Supporter
I think I’d be contacting Holley about that pump failure. There may have been trash left inside the pump‘s brush cavity during assembly. These pumps should be capable of a thousand hours of use without failure. This type of issue may also be indicative of why fuel pumps were moved into the fuel tank and have the fuel itself flowing through the brush cavity to keep things cool.
The Carter fuel pump is cooled by the fuel flowing through it. I discovered this when I tried to use one to pump coolant through a diffusion pump. The electrolysis ate up the brush assembly and a phone call to Carter told me why it happened. The fuel actually fills the inside of the motor case to provide cooling.
 

Rich Kruger

Supporter
I ordered a Carter P4601HP (before I read Howard’s post). I don’t know if the motor is cooled by fuel as indicated by Neil. I’m still going to call Holley as suggested by Randy. The Carter had a lot of reviews that were very positive. Very few were indications of a failure. Fingers crossed.
 
Had 3 brand new Carter HP pumps fail out of the box. All no pressure build up.
After some Google searches the Carter pumps seem to have a bad reputation.
 
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