FAST EFI low fuel pressure

[sprecks]

I installed a FAST EFI system on my car about a year ago. I haven't had any problems up until now. Here lately the engine hesitates sometimes on acceleration and dies when it is idling sometimes. I was under the hood today with the engine idling and looked over at the fuel regulator and noticed the pressure was reading 23 PSI. I tried to adjust it up to the 43 PSI it suppose to be. It would not adjust up no matter how far I run the screw in. So I backed it off and the pressure wouldn't go down either. Once I shut the engine off the pressure dropped to zero. I'm leaning towards rebuilding the regulator then I started second guessing myself and was wondering if this may be a pump problem. What do you think I should check first?

[cudabob496]

are you adjusting the regulator the correct way.
I was doing it backwards once.


http://www.aa1car.com/library/fuel_pump_diagnose.htm

[sprecks]

are you adjusting the regulator the correct way.
I was doing it backwards once.

The direction say to run the adjusting screw in to raise pressure. When that didn't change the pressure I backed it out and still no change in pressure. I'm guessing a broken diaphragm?

[cudabob496]

these guys have a contact number in upper right box:

http://fastmanefi.com/

[sprecks]

Thanks for the link Cudabob.
It gave me some ideas where to look. I'm not holding any residual pressure. When the fuel pump shuts off the pressure goes to zero.

[sprecks]

these guys have a contact number in upper right box:

http://fastmanefi.com/

Thanks, that is where I bought my EFI unit.

[cudabob496]

Thanks for the link Cudabob.
It gave me some ideas where to look. I'm not holding any residual pressure. When the fuel pump shuts off the pressure goes to zero.

http://www.fuelairspark.com/fas/contacts/

[Strawdawg]

close off the return line and see if the pressure goes up and holds once you cut the engine off

If it does, you would appear to need a rebuild kit for the regulator

[sprecks]

close off the return line and see if the pressure goes up and holds once you cut the engine off

If it does, you would appear to need a rebuild kit for the regulator

Thanks Strawdawg. I'll be trying that first thing in the morning. Sure like to know why the regulator may have gone bad. This system only has about 200 miles on it. Coul 10% gasahol be the issue?

[Strawdawg]

Thanks Strawdawg. I'll be trying that first thing in the morning. Sure like to know why the regulator may have gone bad. This system only has about 200 miles on it. Coul 10% gasahol be the issue?

I have not seen one fail that quickly from the alky in the gas.

When the pressure drops that quickly, it can be thru the regulator which is not very common, back thru the fuel pump due to a bad check valve in the pump which is pretty common, or leaky injectors which usually take a few minutes to dwindle down.

Given that the pump was not making much pressure, it kinda sounded like it was not being controlled by the regulator.

Another test you can try is to disconnect the fuel line and feed it into a gallon bucket.  It should fill the bucket with in a minute...or a smaller quantity in a proportionately lesser time.

Also, it is very common for these things to plug a filter very quickly if there is any debris in the tank which is usually associated with an older tank.  This does not account for the fast pressure drop tho.  Sometimes this debris is virtually invisible to the eye so one has to check flow after the filter and then before the filter-or rig a pressure gauge before the filter to see if there is pressure on that side.

[sprecks]

Thanks again Strawdawg. I'll be doing a little more troubleshooting today. I'll be surprised if it is a dirty filter. The whole system was new when I installed it. New tank, fuel lines, pump, filter, regulator and injectors.

[Strawdawg]

It may be the pump, itself, as well.  Not all that uncommon to see on die shortly after delivery.

[gkring]

Sounds like trash in the regulator holding the valve off the seat. If the adjusting screw does nothing it won't be the pump. A bad diagragm will let fuel past it and out through the vacuumn line.  Pull the vacuumn lien off and turn the pump on, engine not running. if fuel shoots out then you have a broken diagragm. if not 99% sure you just have trash in the regulator. Hopefully it is a rebuildable type you can just take apart and clean.

[sprecks]

I've been troubleshooting this morning. First thing I did was checked the fuel filter. It looked brand new. Next I disassembled the regulator. The diaphragm looked good, I couldn't find anything obviously wrong. I reassembled everything and ran the fuel pump. I moved the adjusting screw on the regulator up and down it's full range and could not get more than 20 psi. Now the pressure has actually dropped down to 15 psi.
Next I plugged the outlet of the regulator and ran the pump against the plug. 15 psi max. I think I have pretty much concluded my pump is junk.

Now I'm thinking about going to a smaller pump. I currently have a 400 lph (106 gph) Walbro pump with 3/8" supply and return lines. Maybe the fuel lines are restricting the flow of fuel and this caused the pump to prematurely fail. I'm guessing my engine makes between 500 and 550 HP.  I'm think the Walbro 255 lph pump is probably big enough for my application. What do you guys think?

[Strawdawg]

I would remove the filter and jump the connections so that I could recheck the pressure, but, I suspect you are correct.  I just recall the guy that insisted for a long time that his filter was perfect...and it was plugged up.  Given you have a a new tank, I am pretty sure that the filter is okay, but...been wrong before.

A 255 lph should work