Checking AFR Results
#21
Le Mans Master
Thread Starter
In order to get a reading, I have to remove the schrader valve to allow the fuel to pass into and pressurize the guage.
Other guys a running the same type gauge and post complaining about the gauge not working. All they do to correct this is remove the schrader valve.
Jake
#22
Safety Car
Good post and I think your leson got lost along the way. I agree with you in the fact of not looking at your numbers but rather the fact you did not have a change when you blocked off the line the with the bad FPR, how you blocked it off and what percentage of change you see is kind of irevelent if you know hwta the AFR is when your "normal" FPR is present. Again good post
#24
Le Mans Master
Thread Starter
Good post and I think your leson got lost along the way. I agree with you in the fact of not looking at your numbers but rather the fact you did not have a change when you blocked off the line the with the bad FPR, how you blocked it off and what percentage of change you see is kind of irevelent if you know hwta the AFR is when your "normal" FPR is present. Again good post
Thanks, just trying to share and help.
Jake
#25
Le Mans Master
Thread Starter
#26
Le Mans Master
Thread Starter
That's why posted the procedure I used to test mine to help distinguish my procedure from the gauges others might have.
I decided to post on this primarily because I HAD NO IDEA I had a failed FPR. Engine ran fine. I drive the car everyday and recently returned from the Chicago area and didn't have a single problem or indication that the FPR wasn't up to snuff during the thousand mile drive.
Of course I didn't do any WOT blasts during the trip. I bet that would have cause the engine to go lean. Good thing I didn't.
So my thinking was, "Hey, I wonder how many other guys are experiencing the same thing - bad FPRs and not know it? So, let me post what I found so they can check theirs."
Jake
#27
Racer
Member Since: Aug 2004
Location: Corpus Christi TX
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Quick question for you, JAKE. When reading the fuel pressure with the engine running, how much variation do you normally see (ie how much does the needle wobble)?
#28
Le Mans Master
Thread Starter
I don't know if that's normal or not, never seen anything in writing on that point, but that's what mine does.
Jake
#29
Melting Slicks
Hey Jake,
I took your advice and I tried your pliers trick today.
I had to swap out the hard vacuum tube for a rubber hose that I could squeeze off first. I used a six inch length of rubber vacuum hose for the test.
Note: I had previously raised my fuel pressure setting to 54 psi (without vacuum) a year or so ago by using a nickel under the stock regulator lid.
The results were of no surprise to me. The pliers trick didn't work.
All tests were performed with the car idling using a tpis fuel pressure gauge:
Running normally with vacuum applied: 46 psi.
Running w-hose pinched off with pliers: 46 psi.
This was repeated several times.
With vacuum line removed at regulator (open to atmosphere): 54 psi.
My car pulls about 15" of vacuum at idle.
This was exactly the expected behavior.
My regulator is working properly.
It is worth noting that our cars and regulators are different, mine is an L98 with a factory regulator with a nickel under the lid, it looks like you have a MR with an aftermarket regulator, so these differences may explain the differing results.
The pliers trick is not a reliable method for testing the regulator. Instead, simply pull the vacuum line from the regulator and leave the regulator open to atmosphere when testing.
I suspect that your new working regulator is really leaking vacuum. You may want to check it.
I took your advice and I tried your pliers trick today.
I had to swap out the hard vacuum tube for a rubber hose that I could squeeze off first. I used a six inch length of rubber vacuum hose for the test.
Note: I had previously raised my fuel pressure setting to 54 psi (without vacuum) a year or so ago by using a nickel under the stock regulator lid.
The results were of no surprise to me. The pliers trick didn't work.
All tests were performed with the car idling using a tpis fuel pressure gauge:
Running normally with vacuum applied: 46 psi.
Running w-hose pinched off with pliers: 46 psi.
This was repeated several times.
With vacuum line removed at regulator (open to atmosphere): 54 psi.
My car pulls about 15" of vacuum at idle.
This was exactly the expected behavior.
My regulator is working properly.
It is worth noting that our cars and regulators are different, mine is an L98 with a factory regulator with a nickel under the lid, it looks like you have a MR with an aftermarket regulator, so these differences may explain the differing results.
The pliers trick is not a reliable method for testing the regulator. Instead, simply pull the vacuum line from the regulator and leave the regulator open to atmosphere when testing.
I suspect that your new working regulator is really leaking vacuum. You may want to check it.
Last edited by tequilaboy; 09-15-2007 at 03:21 PM. Reason: typo
#30
Le Mans Master
Thread Starter
I have a 86 with a 415 and a Mini-Ram AND a 96 with a 388 LT1. Both have adjustable fuel pressure regulators. The regulators are a different make and design and are not interchangable. The pliars method works just as I posted on both engines exactly the same way.
If it hadn't worked as I posted, I wouldn't have posted as I did and I would have taken the new Borg Warner adjustable FPR back to O'Reilly's where I bought it for a refund. Why would I keep a FPR that acted no differently than the stock one I removed??
I didn't and don't have a hard vacuum line feeding the regulator and the regulator has a dedicated vacuum line, not 'T'd off. In other words, there is nothing else feeding off the vacuum hose that connects to the regulator. It's a single hose that runs from the intake to the regulator with nothing else attached to it.
I attach the fuel pressure gauge to the schrader valve location with the valve removed.
Just to put this to rest once and for all, I'd like someone who's near Dallas to come by and I'll demonstrate it on both cars. I'll even buy lunch.
I live at 500 Rolling Hills Place, Lancaster, TX, just south of Dallas right off I35E.
If no one takes me up on that offer, I'll take pictures and post the results. This thing seems to have taken on a life of its own.
BTW, there's a very noticable difference in engine performance with the new regulator. Hard to explain, but the engine is quieter, smoother, pulls harder, more responsive and even the exhaust temp leaving the muffler tips on the LT1 is not as hot as before.
Jake
If it hadn't worked as I posted, I wouldn't have posted as I did and I would have taken the new Borg Warner adjustable FPR back to O'Reilly's where I bought it for a refund. Why would I keep a FPR that acted no differently than the stock one I removed??
I didn't and don't have a hard vacuum line feeding the regulator and the regulator has a dedicated vacuum line, not 'T'd off. In other words, there is nothing else feeding off the vacuum hose that connects to the regulator. It's a single hose that runs from the intake to the regulator with nothing else attached to it.
I attach the fuel pressure gauge to the schrader valve location with the valve removed.
Just to put this to rest once and for all, I'd like someone who's near Dallas to come by and I'll demonstrate it on both cars. I'll even buy lunch.
I live at 500 Rolling Hills Place, Lancaster, TX, just south of Dallas right off I35E.
If no one takes me up on that offer, I'll take pictures and post the results. This thing seems to have taken on a life of its own.
BTW, there's a very noticable difference in engine performance with the new regulator. Hard to explain, but the engine is quieter, smoother, pulls harder, more responsive and even the exhaust temp leaving the muffler tips on the LT1 is not as hot as before.
Jake