Mass air flow voltage issues
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From: SW Va
OK, good feedback, sounds like fuel pressure & delivery rate are ok.
On the fuel pressure bleed down, have a listen to the fuel injectors, to see if one or more sound different, then remove the spark plug from that cyl for a deposit read, to see if its wet, or has carbon deposits that indicate its been running rich from a runny nose fuel injector.
Right now, with the test results you've posted it kinda suggests spark should be up there on the suspect list, so the timing light/fuel pressure gauge indicators during a throttle up stall, may provide some more clues to focus the trouble shoot. You may still have more than one problem.
On the fuel pressure bleed down, have a listen to the fuel injectors, to see if one or more sound different, then remove the spark plug from that cyl for a deposit read, to see if its wet, or has carbon deposits that indicate its been running rich from a runny nose fuel injector.
Right now, with the test results you've posted it kinda suggests spark should be up there on the suspect list, so the timing light/fuel pressure gauge indicators during a throttle up stall, may provide some more clues to focus the trouble shoot. You may still have more than one problem.
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Yes truck will drive. I've had it to around 45mph in my neighborhood yesterday. The two things it does it will be driving then fluctuate between 1-2k rpm like it is starved for fuel, whether air or not enough fuel. Or it will be shut down to idle speed while going 45mph and not no amount of acceleration will change it. Once I let off the accelerator it will pick back up. The fuel injection is newer to me but I am thinking it is a intermittent TPS or Fuel pump or both.
The pressure test will only take me so far because it will stay pressurized without fuel. The the leak down is not fast enough. So if the fuel flow stops pressure will remain because it is stuck between pump and fpr. I am going to try flow testing again but that is where I am putting my money.
I did another flow test and the results were not up to par like the first round. I've usually had fuel pumps die. This one may slowly failing making it hard to diagnose.
I do appreciate the help in sorting this thing out.
The pressure test will only take me so far because it will stay pressurized without fuel. The the leak down is not fast enough. So if the fuel flow stops pressure will remain because it is stuck between pump and fpr. I am going to try flow testing again but that is where I am putting my money.
I did another flow test and the results were not up to par like the first round. I've usually had fuel pumps die. This one may slowly failing making it hard to diagnose.
I do appreciate the help in sorting this thing out.
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Ok good news I think. Re-tested the fuel flow through the gauge. I have the gauge with the push button and clear tubing.
30 second this time produced almost no fuel as compared to the first time.
Second flow test today
The bottle is 1qt and should be half full in 30 seconds. This is coming from the schrader valve on the rail. Funny how it tested fine before.
30 second this time produced almost no fuel as compared to the first time.
Second flow test today
The bottle is 1qt and should be half full in 30 seconds. This is coming from the schrader valve on the rail. Funny how it tested fine before.
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Joined: Jan 2004
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From: SW Va
OK, that's good feedback. SO, now go under hood to the power distribution box & remove replace/swap in another like fuel pump power relay, not needed to run the engine, like the AC power relay & see how it goes. The power relays are a known intermittent problem, causing symptoms like you just posted.
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Joined: Oct 2003
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From: SoCal
Ok good news I think. Re-tested the fuel flow through the gauge. I have the gauge with the push button and clear tubing.
30 second this time produced almost no fuel as compared to the first time.
Second flow test today
The bottle is 1qt and should be half full in 30 seconds. This is coming from the schrader valve on the rail. Funny how it tested fine before.
30 second this time produced almost no fuel as compared to the first time.
Second flow test today
The bottle is 1qt and should be half full in 30 seconds. This is coming from the schrader valve on the rail. Funny how it tested fine before.
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That was one of the first things I did (when I got the truck) replaced relay with a bwd one.
That amount was 30sec idling but I did ground anything. Just let the truck run.
That amount was 30sec idling but I did ground anything. Just let the truck run.
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Hope so. Makes since with the surging. Replacing the sending unit is on the list anyhow, so won't hurt to install the complete kit.
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Joined: Oct 2003
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From: SoCal
OOPS again I thought you did the flow test with KOEO & the fuel pump pin grounded.
Hold the EEC4 test plug so the narrow side is up, the fuel pump pin is on the bottom far right.
At KOEO ground that pin & the pump will run until you remove the ground.
As far as basic pressure test just screw on the gauge go to KOEO and it should read around 40 PSI. Turn the key off & watch the needle it should remain steady, if not the check valve in the pump or an injector or the FPR is leaking.
Hold the EEC4 test plug so the narrow side is up, the fuel pump pin is on the bottom far right.
At KOEO ground that pin & the pump will run until you remove the ground.
As far as basic pressure test just screw on the gauge go to KOEO and it should read around 40 PSI. Turn the key off & watch the needle it should remain steady, if not the check valve in the pump or an injector or the FPR is leaking.
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Joined: Jan 2004
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From: SW Va
Ok, now check the electrical connections from say the in cabin inertia switch, to the fuel tank for corrosion, damaged wiring or electrical connector problems, under load voltage drop, to make sure the pump is getting a good solid operating voltage without interruption, or voltage drop.
I don't know what to make of the latest volume tests. If the engine was running & the gauge indicated you had fuel pressure, you should have gotten fuel out the gauge bleed hose when pressing its pressure release valve.
Postmaster
Joined: Oct 2003
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From: SoCal
Do the second test that i mentioned in my last post and watch the gauge for 10 minutes.
If the gauge leaks down key off then you have found your problem and you dont need do a proper leak down test.
If the gauge is steady then you need to do the flow test correctly.
If the gauge leaks down key off then you have found your problem and you dont need do a proper leak down test.
If the gauge is steady then you need to do the flow test correctly.
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New info today with pics and video. So I haven't messed with it since my last post, left the pressure gauge on it and today the about 10psi
Here is a video of the flow test I performed and a video of the truck running and surging. Of coarse it get worse under load. Just click on image to watch.
Now for the good part, I lifted the bed tonight so I can replace the fuel pump/sending unit tomorrow. I found this on the gas tank right over the fuel unit.
So with all the bird crap over the years it's a very good possibility the wires could be badly corroded and the steel lines are pretty rust on top. But this can definitely be the problem. Should know more tomorrow.
Any recommendations on a pump/unit local house carries spectra or airtex. Any preference??
Here is a video of the flow test I performed and a video of the truck running and surging. Of coarse it get worse under load. Just click on image to watch.
Now for the good part, I lifted the bed tonight so I can replace the fuel pump/sending unit tomorrow. I found this on the gas tank right over the fuel unit.
So with all the bird crap over the years it's a very good possibility the wires could be badly corroded and the steel lines are pretty rust on top. But this can definitely be the problem. Should know more tomorrow.
Any recommendations on a pump/unit local house carries spectra or airtex. Any preference??
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Ended up ordering a delphi pump/sender unit, so have to wait for it to get here. I did unplug the unit today and the connections looked good, tested voltage to pump and a little over 12v so good there, hooked a 3/8 line to outlet and flow tested which it was fine there so I am not sure why it is different pending location. Put my pressure gauge on the pump outlet and put it to 50psi, 5 hours later it is now at 30psi and still appears to be slowly dropping. Im going to let it sit a little longer then take out the pump and see what it looks like.