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304 CJ7 Proper fuel filter with a Holley 804-12 fuel regulator - PSI issues !!

6K views 61 replies 9 participants last post by  jeep_boy02 
#1 ·
Hello I recently installed a Holley 804-12 fuel regulator in my CJ with a 304 - the issue is the stock 3 port fuel filter will not allow the adjustment of the fuel pressure because the fuel filter has the vent/return port on it. With that port open the fuel pressure is close to zero and when crimped I am able to set the fuel pressure as it should be. Can anyone recommend a 2 port in/out fuel filter that can be used in this setup. FYI the CJ runs 100% better at idle and cruise with the vent/return port crimped which means the carburetor is receiving the proper fuel pressure.

Setup - Fuel tank >> mechanical fuel pump >> 3 port stock fuel filter >> 1 port to the Holley regulator/ 1 port to the vapor line back to the tank >> motorcraft 2150 carburetor

Anyone that has first had experience with this issue would be helpful

Thanks in advance
 
#2 ·
HI, You should NOT need a pressure regulator for a mechanical fuel pump.. they only deliever 3 to 5 lbs of pressure and a carb should handle that..
What kind of problems are you having that you think you need a regulator? The return line on the filter is to aid in stopping vapor lock by keeping the fuel moving and cool.
good luck
tim
 
#3 ·
Actually, this isn't quite correct. The stock mechanical fuel pump should provide around 7-8 psi with no return line hooked up. With the return, it should make 4-5 psi, which is what the carb wants. If the OP's pump isn't showing these numbers, then either the pump is failing or he's got a leak somewhere.

I do agree, however, that a fuel pressure regulator shouldn't be necessary with the OEM style bypass filter and mechanical pump.

Matt
 
#4 · (Edited)
the mechanical pump is irregular in its fuel psi delivery by nature ranging from 3-6 psi which makes the vehicle run rough when starved and rich when at high. To eleviate the problem a regulator is the key to make the delivery equal at 3 which is what the carburetor needs to perform correctly. I tested the pressure with the fuel filter, without the regulator to confirm the irregularity in pressure and it actually delivered between 1-8 PSI - Note: this is a new operable fuel pump functioning as it should. This is old technology when fuel consumption and emissions was not as big an issue. I need a tested solution to provide an answer to keeping the regulator in play.

As stated the engine runs 100% better with the regulator installed while crimping the return line. If I remove the crimp the engine runs rough at idle and cruise

Also the fuel pressure is 3 constant at the carb with the return crimped

Thanks for your comment - need a solution - please feel free to post comments if applicable to the topic
 
#26 ·
I tested the pressure with the fuel filter, without the regulator to confirm the irregularity in pressure and it actually delivered between 1-8 PSI
I'm not sure why everyone is so quick to discount a bad fuel pump, or a leak in the system. I'm pretty sure the fuel pressure should NOT bounce around from 1-8 psi with the factory filter/return setup.

Hopefully my videos were helpful to demonstrate this.

Matt
 
#5 ·
My mechanical fuel pump holds a *steady* 4.5 psi with the return hooked up. I can shoot a video of my pressure gauge, if you don't believe me.

The return line is designed to eliminate the pulsating nature of the pump. The needle and seat in the carb are also designed to tolerate slight pressure fluctuations.

You said the pressure is "close to zero" with the return line open. That is not normal, and it leads me to believe either your pump is bad, or you have a leak in the system.

Matt
 
#7 ·
Hi, If your having problem with the fuel pressure on a mechanical pump then I'd look at float level in the carb. maybe the carb is due for a rebuild.
Fuel pressure does NOT regulate fuel consumption .... fuel comsumption is regulated by the carb size, jets, metering rods and a heavy rt foot.
good luck
tim
 
#8 ·
I think you're complicating an issue rather than taking care of the root problem. Remove the FPR. A carb float system is there to maintain proper fuel levels in the carb regardless of the spikes in fuel delivery.
 
#9 · (Edited)
brand new carb and pump ( everything is new ) adjusted by a professional so the carb is out of the equation - this return line although necessary is a pain in my butt.

To paint a clear picture

setup = new fuel tank >>new mechanical pump >> new stock 3 port fuel filter ( 1 out to regulator / 1 out to return ) >> new 804-12 Holley regulator >> new 2150 motorcraft carb

Symptoms with return line open - rough idle and cruise / rich fuel smell at the exhaust

Symptoms with return line crimped - smooth idle / less fuel smell at the exhaust

Tests # 1 - pressure gauge tested the fuel line with the stock fuel filter without the regulator- psi reading 1-8 irregular - engine rough idle and cruise
# 2 - pressure gauge tested the fuel line at the regulator ( second out port on the regulator ) with stock fuel filter return line open and regulator installed = 0 psi - no pressure due to open return - engine idle and ran rough at cruise - my thinking is that the reading is zero because the return line is open
# 3 - pressure tested the fuel line at the regulator ( second out port on the regulator ) with the stock fuel filter return line crimped and regulator installed = 3 psi constant - engine ran smooth at idle and cruise

Prognosis thus far - with the return fuel line crimped the engine ran as it should with constant 3 psi - my concern is a vapor lock and/or a burst in the fuel pump diaphram. Question - assuming the pressure is irregular from the pump and the regulator is controlling the amount of fuel being sent to the carb at 3 psi - without the return line in place would this create a potential problem ? if so what problems and is there a solution to keep the regulator in place?? I have seen many muscle cars with a in/out fuel filter and have never heard of anyone having issues.

Thanks for your comments
 
#10 ·
brand new carb and pump ( everything is new ) adjusted by a professional so the carb is out of the equation - this return line although necessary is a pain in my butt.

To paint a clear picture

setup = new fuel tank >>new mechanical pump >> new stock 3 port fuel filter ( 1 out to regulator / 1 out to return ) >> new 804-12 Holley regulator >> new 2150 motorcraft carb

Symptoms with return line open - rough idle and cruise / rich fuel smell at the exhaust

Symptoms with return line crimped - smooth idle / less fuel smell at the exhaust

Tests # 1 - pressure gauge tested the fuel line with the stock fuel filter without the regulator- psi reading 1-8 irregular - engine rough idle and cruise
# 2 - pressure gauge tested the fuel line at the regulator ( second out port on the regulator ) with stock fuel filter return line open and regulator installed = 0 psi - no pressure due to open return - engine idle and ran rough at cruise - my thinking is that the reading is zero because the return line is open
# 3 - pressure tested the fuel line at the regulator ( second out port on the regulator ) with the stock fuel filter return line crimped and regulator installed = 3 psi constant - engine ran smooth at idle and cruise

Prognosis thus far - with the return fuel line crimped the engine ran as it should with constant 3 psi - my concern is a vapor lock and/or a burst in the fuel pump diaphram. Question - assuming the pressure is irregular from the pump and the regulator is controlling the amount of fuel being sent to the carb at 3 psi - without the return line in place would this create a potential problem ? if so what problems and is there a solution to keep the regulator in place??
The problem as I see it is, all your symptoms point to a weak or failing fuel pump, assuming your system isn't leaking. I've had new fuel pumps that didn't hold pressure right from the box.

As I stated, 1-8 psi with the factory return line setup isn't normal. Nor is zero pressure after simply installing a FPR to the factory setup.

How have you tested for leaks? Tell me this, does the fuel pressure stay at 3 psi for a while after you shut the engine off? Or does it quickly drop to zero? My system will hold pressure overnight, gradually dropping from the operating pressure of 4.5 psi to around 2 psi in the morning.

edit: I should add, be sure to pinch the return line when you do the shut-down test above.

Matt
 
#11 ·
I am going to test it this afternoon again and report back - I will do the same tests as before and monitor the pressure to see if it holds after shut down.

How do these fuel filters work?? do they build pressure to a certain pressure and release the excess pressure ?? if so what is telling the filter how much fuel should be dispensed if it is greater than what the carburetor needs? not familiar with this setup ?? it would seem to me with the return line or port open the pressure would be irregular ?? What am I missing - with a line open how can pressure be equalized?
 
#12 ·
I am going to test it this afternoon again and report back - I will do the same tests as before and monitor the pressure to see if it holds after shut down.

How do these fuel filters work?? do they build pressure to a certain pressure and release the excess pressure ?? if so what is telling the filter how much fuel should be dispensed if it is greater than what the carburetor needs? not familiar with this setup ?? it would seem to me with the return line or port open the pressure would be irregular ?? What am I missing - with a line open how can pressure be equalized?
The mechanical pump should operate at around 7-8 psi with no return line. When operating, it fills the entire filter with fuel. The orifices of the filter are metered (different sizes) so that a little over half of the 7-8 psi goes to the carb, and the rest goes to the return. Notice how the supply nipple (center hole) of the filter is larger than than the return nipple.

The bypass filter is basically a simple fuel pressure regulator, and it helps prevent vapor locks, as it is also a vent for the system.

Matt
 
#13 ·
Hi, There is NO restriction on the filter its just a paper filter element and it can be blown thru with no problem.. Now ONE line (return line) is smaller in order to keep fuel pressure, out of all the Jeeps with this filter set up (95%) and are having NO problem Don't you think there may be another issue causing the problem .. A NEW carb installed does NOT include adjusting the float level only air/fuel and Idle (they can be wrong from the factory and even stuck in one position). as well as a bad pump from the factory.
Matt1981CJ is very knowledgeable.
good luck
tim
 
#14 ·
Matt then why do I get no pressure reading on the Holley with the fuel filter in place and not crimped? and a reading when the line is crimped? Further why does the engine run as it should - smooth at idle and cruise with the line crimped? If the fuel pump or carb were defective or set incorrectly I would think the engine would run the same regardless of the setup??

Not challenging any ones knowledge just trying to better understand the logic

Lets keep it rolling

Thanks
 
#15 ·
With adding the fuel pressure regulator into the system after the 3 port filter, the fuel is taking the path of lest resistance, ie, the return to the tank. The pressure regulator is causing too much of a restriction to get pressure/fuel to the carb thus you having to crimp off the return line to get pressure at the carb. The 3 port filter is kind of a hack way to regulate pressure as it expects the smaller return line to give enough resistance to keep enough pressure going to the carb to keep the fuel bowl full, but it does a decent job and does keep the fuel circulating to help with vapor lock issues in a poorly designed system. Gmann777, you can run any standard 2 port 5/16th's fuel filter and plug the return line and use your new regulator.

https://www.napaonline.com/napa/en/p/FIL3032/FIL3032_0227838168

Now it can be argued that you should use a return style fuel pressure regulator as not to make the mechanical pump deadhead/internally bypass, but mechanical pumps ran for years and will continue to run in this configuration.
 
#16 ·
Agree as mentioned previously I see in/out fuel filters with regulators in muscle car rebuilds all the time with no issues. However I read on some blogs how some people have experienced blown diaphragms in there pumps. The real question is if the mechanical pump send 6 psi to the regulator and I want 3 psi to the carb will that 3 psi difference create a big enough problem?
 
#21 ·
I agree the pump is probably fine. If pinching the return line builds pressure then the system is operating correctly. The FPR needs to be removed OR replace the filter with a simple in/out version.

The real question is if the mechanical pump send 6 psi to the regulator and I want 3 psi to the carb will that 3 psi difference create a big enough problem?
If I understand your question: These pumps are NOT positive displacement. In other words they will happily cycle all day long with no fluid flow/movement (within reason because of heat buildup).
 
#17 ·
The real issue right now is your system isn't producing enough pressure. 3 psi with the returned blocked says it all. Zero pressure with FPR and return open confirms it.

The cause of the lack of adequate fuel pressure is yet to be determined.

I know you're hoping to hear a different answer, but....

Matt
 
#18 ·
There is nothing at all wrong with his fuel pump. The regulator he purchased is factory set at 2.7psi and therefore he is getting the correct fuel pressure post regulator with the return line crimped off. When he opens the return line he is getting no pressure post regulator because fuel is taking the path of least resistance, the return line. There is nothing in the factory system that regulates pressure and nothing that would create enough pressure with the return line open to build enough pressure and force fuel through the regulator. As I mentioned before, Gmann777 can use a standard 2 port filter and the regulator and get a constant 3psi at the carb. he will not have an issue with the factory pump as it will bypass internally and function fine. The only time you have issues with blowing out the diaphragm in the fuel pump is if you have a high flow/high pressure aftermarket pump and no return line out of the regulator.
 
#20 ·
There is nothing at all wrong with his fuel pump.
I don't think we can jump to that conclusion, yet. He said his fuel pressure jumps from 1-8 psi with the factory filter/return setup. I don't think that is normal or correct. Here is mine running with the return hooked up. Notice it's holding steady just above 4 psi.



Here in mine running with the return line pinched. Notice it's holding steady around 7 psi. The OP's isn't even close to this.



And finally, here is mine with the engine shut off and the return line still pinched. Notice it's holding pressure, although it's gradually falling. I suspect it's dropping gradually because I didn't get a full pinch on the return line with my vice grips. We don't know if the OP's system holds pressure with the engine off, yet.



None of this proves the OP's fuel pump is bad, but I think it's pretty clear his fuel system isn't creating the pressure it should. Hopefully, it's something simple, like a loose hose clamp, or a pin hole leak in a rubber fuel line. But I don't think we can rule out a failing pump, either.

Matt
 
#19 ·
I'm having the same problem OP and I have tried various pump set ups, mechanical and electric and both at the same time and still having a problem. I'm thinking the issue is in the tank or lines. I have also had my tank out and replaced the sock, rubber lines, etc.

One thing to check before you go further is look inside the return outlet of your fuel filter, there should be a smaller hole inside the large hole. I bought a filter from advance and it was wide open, and went to autozone and it had the restriction built inside the return outlet.

This did not correct my problem however but worth checking.

Let's keep each other informed on finding a solution!
 
#23 ·
What would be a good way for the OP and I to test the fuel system for leaks before dropping the tank?

I was thinking abt pulling the hose off the fuel pump inlet and putting a clamp on the rubber hose at the back if I can get to it, and blowing compressed air in the line and looking/listening for leaks. Or another option would be to use a vacuum pump and see it it holds x amount of vacuum.
 
#25 ·
One thing that hasn't come up so far is the return line orientation which should be at the 12 o' clock position and making sure that you do in fact have the outlet ports hooked up correctly. Center port to the carb and 'top' port as the return.

When my pump was failing it would sputter and almost die. With a new pump and OEM style filter it has more than enough fuel and starts right up even after sitting.
 
#27 ·
Matt1981CJ7 said:
I'm not sure why everyone is so quick to discount a bad fuel pump, or a leak in the system. I'm pretty sure the fuel pressure should NOT bounce around from 1-8 psi with the factory filter/return setup. Hopefully my videos were helpful to demonstrate this. Matt
I'm not necessarily leaning toward a bad pump. If the return was on the bottom or the center port was connected to the return instead of the outer port fuel would be draining off and not going to the carb. I'm just guessing since I haven't seen how it is hooked up.
 
#29 ·
The point is, the fuel pressure should stay constant at 4-5 psi with the OEM filter return line open and around 7-8 psi with the return line blocked. It should not bounce around from 1-8 psi in any configuration.

At least that has been my experience with my 360 and 258 engines equipped with the OEM fuel setup.

Matt
 
#30 ·
OK resolved I decided to abandon the stock 3 port setup and purchased an in out fuel filter. I set my psi to 3 and its running like a charm. I visited a well known mechanic in my area and he said dump the stock fuel filter. He said the old stock filter was a bogus way of attempting to regulate fuel pressure and made it more difficult to properly tune any engine including the carb. If I have issues I will report them here otherwise the engine is running much better without the stock filter and with the fuel regulated at 3 psi. Thanks for all your help and this was a good topic to discuss

Cheers
Gary
 
#32 ·
From my experience I would agree with Matt
The tank, the pickup, the hard lines, rubber lines, the vent tubes, the charcoal canister, having lines hooked up wrong to the carb, filter orientation, and bad fuel pump are all issues I had when I first got my CJ. Not to mention the Carb itself. I like to start at the tank and work my way from there. Especially with the pump gas we have today I would change the rubber lines at a minimum with the rubber hose that can withstand ethanol.

I also had a time once where I just got bad gas and it was only resolved after running all new gas through it. Also not to mention gas that has sat for any length of time.
 
#37 ·
I wonder if he had the return nipple hook up to his carb? OH well Try that Matt and see what kind of reading you get?
take care tim
It doesn't matter to me that much.

The whole point of me posting those videos was to demonstrate how the bypass fuel filter acts as a fuel pressure regulator, and to show that the fuel pressure should not jump around as the OP claimed his does.

Apparently those points fell on deaf ears, since the OP was just looking for validation of his band-aid fix.

Oh well, indeed.

Matt
 
#38 · (Edited)
OK I mentioneed earlier that I would confirm the tests again and here are the results

To paint a clear picture

setup = new fuel tank >>new mechanical pump >> new stock 3 port fuel filter ( 1 out to regulator / 1 out to return ) >> new 804-12 Holley regulator >> new 2150 motorcraft carb

Symptoms with return line open - rough idle and cruise / rich fuel smell at the exhaust

Symptoms with return line crimped - smooth idle / less fuel smell at the exhaust

Revised Test reults

Tests # 1 - pressure gauge tested the fuel line with the stock fuel filter without the regulator-psi reading 6-8 irregular - engine rough idle and cruise - this carburator requires 3 psi so sending 6-8 was to excessive and made the engine run rough. The factory sets up the carburetor to run at 3 psi so sending more fuel to it will only complicate the tuning of the carb.
# 2 - pressure gauge tested the fuel line at the regulator ( second out port on the regulator ) with stock fuel filter return line open and regulator installed = 1-5 psi - insufficient/irregular pressure due to open return - engine idle and ran rough at cruise
# 3 - pressure tested the fuel line at the regulator ( second out port on the regulator ) with the stock fuel filter return line crimped and regulator installed = 3 psi constant - engine ran smooth at idle and cruise

Prognosis thus far - with the return fuel line crimped the engine ran as it should with constant 3 psi

Fix - on the recommendation of a old school experienced local mechanic who witnessed the test and setup he suggests to remove the stock filter with an inline in/out filter and regulate the pressure at 3psi with the Holley 804-12 regulator. His opinion is that the stock filter was an old school way to attempt to regulate the fuel pressure by sending an unbalanced amount of fuel to the carb and dumping the unused excess fuel back to the tank. This is because the irregularity of the pressure the mechanical fuel pump supplies. When I asked about the removal of the return line he said it wasn't necessary as the excess pressure from the pump wasn't enough to be concerned about. He has converted too many of these to question him so this is not a band aid approach - as long as the engine performs as it should without the rough idle and cruise I am happy. For me regulating the fuel is what fixed my issues.

Bottom line - My fuel pump operated as it should, stock fuel filter ok if your setup runs smooth and does not burn excess fuel - mine did not, abandon the stock fuel filter and replace it with a in/out filter and use the Holley 804-12 regulator set at 3 psi - runs like a charm



Thanks for your comments
 
#39 ·
Tests # 1 - pressure gauge tested the fuel line with the stock fuel filter without the regulator-psi reading 6-8 irregular - engine rough idle and cruise - this carburator requires 3 psi so sending 6-8 was to excessive and made the engine run rough. The factory sets up the carburetor to run at 3 psi so sending more fuel to it will only complicate the tuning of the carb.
Nope! If your carb cannot handle the variations listed in fuel pressure you have a float and needle/seat issue. You are overfilling your bowl. You have an extremely fancy band-aid installed on your Jeep now.
 
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