Fuel Bad fuel pressure regulator?

91GTstroked

15 Year Member
Jun 14, 2007
429
236
63
Hey guys,

Hopefully found the issue to my problems. Since I bought the car, I felt it always took longer than it should to start. I also had to raise the fuel pressure a couple weeks ago, as it was down to 20 with the car running. Idles pretty rough to

The car has a kirban fuel pressure regulator. When I turn the ignition on, but don't start the car the fuel pressure drops fast. Shouldn't it hold pressure? Also I can smell fuel in the vacuum line.

You can hear the fuel pump prime just fine. I did just order a new one. Below is a video.


View: https://youtu.be/6ruNK-iWgsM
 
  • Sponsors (?)


I have a Kirban FPR. The diaphragm has a check valve (anti-siphon valve).
631907
 
  • Like
Reactions: 1 user
I have a Kirban FPR. The diaphragm has a check valve (anti-siphon valve).
631907
I kinda wish I didn't order a new one. Didn't know that they can be rebuilt. Looks like that part is around 30 dollars? I could always have my old one rebuilt and then keep a spare.

I should get around to installing it this weekend. Hopefully it's the culprit.
 
It should look exactly like the picture.
Raised & bubbled, not good.
Need pic.
There's a small spring behind the metal piece.
Got the new one installed. This one was holding pressure long after the car was shut off. My old one would be down to zero in less than a minute. I set the fuel pressure at 40 psi with vacuum line off. I have no idea what it's suppose to be.
 
Vacuum line off & plugged, set to 40 psi.
Vacuum line connected, it will read about 35 psi.

I bet it starts right up, hot or cold.
I initially put it at 40, but it smelled pig rich and could see what looked like fuel coming out the tail pipe. So I back it down to 37-38 and much better.

I need to get a/f checked out.
 
I initially put it at 40, but it smelled pig rich and could see what looked like fuel coming out the tail pipe. So I back it down to 37-38 and much better.

I need to get a/f checked out.
If you don't have working catalytic converters, the exhaust is going to stink, and it may smell like unburned fuel.

If you didn't get codes 41/91 or 42/92 from the code dump with a relatively stock engine, your A/F ratio is probably good enough as is.

Water is a product of combustion in all internal combustion engines.
If you see small amounts of liquid dripping from the tailpipe, it probably is condensation. The clue is that the condensation only appears on a cold engine start.

If you see more than a small amount of water on a hot or warm engine, you may have a leaking head gasket, Do a cylinder balance test to find the offending cylinder.


Cylinder balance test: use this to find dead or weak cylinders:

Revised 09-Sep-2017 Added reminder to write down the stored codes and engine running codes.

The computer has a cylinder balance test that helps locate cylinders with low power output. You’ll need to dump the codes out of the computer and make sure that you have the A/C off, clutch depressed to the floor and the transmission in neutral. Fail to do this and you can’t do the engine running dump codes test that allows you to do the cylinder balance test.

Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

Be sure to turn off the A/C, have the clutch depressed to the floor, and put the transmission in neutral when dumping the codes. Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.


Here's how to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

583775.jpg


583776.jpg


If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

583777.gif


The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

583778.gif


The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.


WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems.
This is crucial: the same wire that provides the ground to dump the codes provides signal ground for the TPS, EGR, ACT and Map/Baro sensors. If it fails, you will have poor performance, economy and drivability problems

Some codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Dumping the Engine Running codes: The procedure is the same, you dump the codes and then you start the engine with the test jumper in place. Be sure the A/C is off, clutch depressed to the floor and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

Your 86-88 5.0 won't have a working Check Engine Light, so you'll need a test light.
See AutoZone Part Number: 25886 , $10
583779.jpg




Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see www.midwayautosupply.com/Equus-Digital-Ford-Code-Reader/dp/B000EW0KHW Equus - Digital Ford Code Reader 3145.
It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $22-$36.
Order it at Walmart for a better price and free shipping
583780.jpg


Write down the codes that the computer outputs since they will give you information on problems that are stored in the computer's memory


Cylinder balance test


If you have idle or IAC/IAB problems and the engine will not idle on its own without mechanically adjusting the base idle speed above 625-750 RPM, this test will fail with random cylinders pointed out every time it runs. The IAC/IAB must be capable of controlling the engine speed to run in the 1300-1500 RPM range. Playing with the base idle speed by adjusting it upwards will not work, the computer has to be able to control the engine speed using the IAC/IAB.

Warm the car's engine up to normal operating temperature. With the test jumper in test position, start the engine and let it stabilize. It should flash a 10 and then a 4 and maybe an 11. If no 11, then there are other codes that will be dumped.

Write down the codes that the computer outputs since they will give you information that the computer found when it is running. These are often different from the stored codes.

One of the first tests it does is to open the EGR all the way, this will cause the engine to stumble and almost die. If the engine dies here then you have EGR problems.
To start the cylinder balance test, briefly floor the accelerator past 2500 RPM and let off the accelerator. The engine will stabilize at about 1300-1450 RPM and the cut off the fuel injectors one at a time. The engine speed will drop briefly and the computer will turn the fuel injector for the cylinder under test back on. Then it starts the process for the next cylinder. When it has sequenced through all 8 injectors, it will flash 9 for everything OK, or the number of the failing cylinder such as 2 for cylinder #2. Quickly pressing the throttle again up to 2500 RPM’s will cause the test to re-run with smaller qualifying figures.
Do it a third time, and if the same cylinder shows up, the cylinder is weak and isn’t putting out power like it should. See the Chilton’s Shop manual for the complete test procedure

See
View: https://www.youtube.com/watch?v=HDXrkKS4jTE
for a visual tour through the process. There is no voice narration so you have to listen carefully for the engine sounds. I posted the link for the benefit of Stangnet members who had questions about how to do a cylinder balance test. I do not own that video and I am not the creator.

Do a compression test on all the cylinders.
Take special note of any cylinder that shows up as weak in the cylinder balance test. Low compression on one of these cylinders rules out the injectors as being the most likely cause of the problem. Look at cylinders that fail the cylinder balance test but have good compression. These cylinders either have a bad injector, bad spark plug or spark plug wire. Move the wire and then the spark plug to another cylinder and run the cylinder balance test again. If it follows the moved wire or spark plug, you have found the problem. If the same cylinder fails the test again, the injector is bad. If different cylinders fail the cylinder balance test, you have ignition problems or wiring problems in the 10 pin black & white electrical connectors located by the EGR.

How to do a compression test:
Only use a compression tester with a screw in adapter for the spark plug hole. The other type leaks too much to get an accurate reading. Your local auto parts store may have a compression tester to rent/loan. If you do mechanic work on your own car on a regular basis, it would be a good tool to add to your collection.

With the engine warmed up, remove all spark plugs and prop the throttle wide open with a plastic screwdriver handle between the throttle butterfly and the throttle housing. Crank the engine until it the gage reading stops increasing. On a cold engine, it will be hard to tell what's good & what's not. Some of the recent posts have numbers ranging from 140-170 PSI. If the compression is low, squirt some oil in the cylinder and do it again – if it comes up, the rings are worn. There should be no more than 10% difference between cylinders. Use a blow down leak test (puts compressed air inside cylinders) on cylinders that have more than 10% difference.

I generally use a big screwdriver handle stuck in the TB between the butterfly and the TB to prop the throttle open. The plastic is soft enough that it won't damage anything and won't get sucked down the intake either.

A battery charger (not the trickle type) is a good thing to have if you haven't driven the car lately or if you have any doubts about the battery's health. Connect it up while you are cranking the engine and it will help keep the starter cranking at a consistent speed from the first cylinder tested to the last cylinder.
 
Last edited:
Thanks I didn't get any of those codes. The car has gt40x heads, e cam, 1.7 rockers.

I have that scan reader, getting smog codes and egr codes doing a keor. Both deleted and no cats.

It probably is only condensation, it only happened on a cold start up.
 
Last edited:
I also have a kirban fpr. When I prime the fuel pump my fuel pressure stays at zero but it starts up fine and I get about 38psi with vacuum hose off. Sometimes I get a hot start stall. Is my fuel pressure suppose to stay at zero when I prime the fuel pump?