EFI Fuel Pressure Issues - Replace Pump?

[Izzy]

I'm chasing a fuel pressure engine on my 5.0 EFI engine. I have the BC 23 gallon tank with in tank pump.

I'm only getting between 24 and 30 PSI of fuel pressure at the rail and I think it is what is causing my hesitattion issues.

I have already changed the filter and the Fuel pressure regulator and the issue continues so I'm assuming i have a fuel pump issue.

Everything I have read says that I need a pump that will produce 40-50 gallons\hour of fuel rate and it needs to provide the 40 psi of pressure it needs.

The question I have is which fuel pump should I get? I read that the 86 mustang fuel pump is what is in the BC tank and should work but the specs on that pump says it only provides 23 gallons/hour of fuel rate.

What pump should I get?

Is there anything else I should be checking?

 

[Broncobowsher]

Pinch the return line with the engine running. Pressure should spike to 60+ If it does, you have a bad regulator.

If the pressure stays low I would suspect a supply problem (possibly the pump). Does the pressure drop off when under load (driving)?

 

[73azbronco]

^^^ This.

If the pressure stays low after pinching off the return, you may also have a stuck open/leaking injector. Low flow may mean clogged filter or bad pump.

Most Haynes manuals for a 90ish mustang/explorer will give you a step by step procedure to chase down faults.

 

[ScanmanSteven]

Have you checked the sock/filter on the pump? Some of those tanks had problems with residue in the tank, clogging the sock. I've had mine off more times than I can remember, but I cut a small hole in the bed to access the top of the tank and would highly recommend it rather than pulling the tank, again.

 

[Izzy]

Thank you for the tips guys. I will do the pinch test bu after replacing the regulator, I'm pretty sure it is not the issue.

I have not yet looked at the sock filter as I have not dropped the tank yet. Was wanting to test everything else I could before doing that.

 

[Izzy]

Can anyone help me with my questions about which fuel pump to use as a replacement?

 

[Izzy]

Took the tank out and it was very dirty so I think the strainer is definitely needing replacement.

Is there anyway to test the pump before putting it all back together?

 

[Izzy]

Well this is getting frustrating. I pulled the tank and replaced the strainer which was definitely dirty. Put it all back together and sure enough, same issue. I'm only getting 24-28 psi at the fuel rail.

Only thing left is the pump. Any suggestions on which pump to get?

 

[needabronco]

BCB uses a standard efi Mustang pump. I replaced mine after a few thousand miles and discovered that there wasn't an adequate ground to the pump. I doubled up the ground making sure I had bare metal on the tank and the frame and my problem was solved. I would also recommend changing the filter out after a couple hundred miles just to be safe. Those tanks are a pain to pull on the side of the highway!

 

[Izzy]

Question about the mustang pumps. I have read that the pump should move 40 gallons per hour. The mustang pumps say they move 23 gallons per hour. Will the mustang one work or do I need to find one that specifically pumps over 40 gallons per hour?

 

[chuzie]

I don't understand why the spec is 40gph. If 23gph was good enough for a mustang, why would it not be for our Broncos running mustang engines? Where did you rear 40gph?

 

[Izzy]

I read it on the BC site.
http://www.bcbroncos.com/fuelefi.html

"This pump is a standard replacement mustang fuel pump and filter strainer so the fuel pressure (40 psi) and flow rate (40-50 gph) are exactly what you need when doing an EFI swap."

 

[chuzie]

Gotcha. Usually when I see a spec, I bend over backward trying to match it until someone slaps me on the back of the head to see the tress from the forest.

Let's look at this logically. Is it really possible for your engine to consume fuel at such a high rate (40GPH) that you run the risk of losing pressure? No. Hell, I don't think it is possible for these engines to consume 23GPH unless highly modified for the strip let alone 40GPH. I am willing to bet $$$ that is a typo on the BC site.

If your engine is sucking a tank of fuel (23gal?) every 35 minutes, you have bigger issues than the fuel pump.

I run the E2000 HP pump rated at 40GPH and the carter p4070 rated at 72GPH which makes my previous statement unreliable but look at it in terms of MPG instead of GPH.

My 351EFI sucks 9MPG on the highway at 65MPH. That is 7.2GPH at 2,100 RPM. Imagine what it would take to get to 40GPH.

BC should be open now. Give them a shout. Oh, wait. They have implemented their new "Tech" hours. Now you get to wait most of the day before you can call them, along with everyone else at the same time, to ask a technical question about one of their products.

 

[Izzy]

Chuzie,

I had considered to point about the gph as well and wondered if it really was necessary. At the same time though, I have seen some parts sites list one pump at 23 gph and another at 40 gph. As long as the PSI is 40, I would think it's ok.

Now with all this said, it is possible that the pump is not my issue. Any suggestions on how to test\confirm if I have a bad pump versus a leaky lifter or something?

 

[chuzie]

Did you ever do the pinch test? Does your fuel pressure remain stable after engine is off?

 

[Izzy]

Once the engine is off, my fuel pressure lost maybe 2-4 psi over the course of 2-3 days. It then stabilized at around 20 psi and stayed there.

 

[chuzie]

Mine does the same. It is the pump that retains the pressure when the engine is off. Some stay at 40psi and others 20psi. I think it is variable with pump design or condition; not sure.

Since your pump is in the tank and you are holding pressure, it is reasonable to conclude you have no leaks from the pump to the fuel rail.

Do that pinch test and let us know your PSI reading.

 

[Izzy]

ok, about to wrap up a meeting and will then run out there and test that pinch test again

 

[EricLar80]

When you are testing the pressure, do you have the vacuum line removed and plugged? If not, you could be measuring the regulator doing its thing - regulating pressure vs the intake vacuum...

Remove and plug the vacuum line to see if you get the full 39.15 psi to make sure the regulator is working.

Plug the return fuel line to verify the pump is capable of delivering more than 40 psi.


Eric

 

[Izzy]

Ok, did the pinch test 2 ways and got 2 results.

1. I pinch the fuel line before starting the engine. Engine cranked over, ran for a few minutes and then the pressure began dropping very low and died.
2. I then unpinch the line and cranked the engine again. Engine ran at 24-28 psi. Then pinched the line again and noticed no change.

I will test the vacuum plug test now.