Runs rich,suspect fuel problem
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Junior User
Joined: Feb 2004
Posts: 87
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From: St.Paul, MN
Runs rich,suspect fuel problem
I need some new ideas.
This problem has been getting progressively worse and I must install a cleaned set of plugs to get 30-40 miles.
I replaced the aftermarket EGR valve (had condensation inside that froze when cold, holding it open at idle) with the original unit I took off some years back while I was chasing another problem. That problem was leaks in intake/exhaust gaskets...I just left the "new' Tomco EGR valve on after repair.
At the same time I did this, I also pulled the Carter YFA (non feedback) carb and cleaned it up a bit. I also installed a new needle valve and seat. I set the float as best I could. The brass float (I am not the original owner here but have had this truck for 100M)was not leaking (no fuel inside) but had a dent on the side and the stem was twisted. I straightened it before reinstall.
I checked the PCV...rattles ok
I swapped out the cap, rotor, plugs and wires with known "good" used items that I had from a previous "tune up". more to come
This problem has been getting progressively worse and I must install a cleaned set of plugs to get 30-40 miles.
I replaced the aftermarket EGR valve (had condensation inside that froze when cold, holding it open at idle) with the original unit I took off some years back while I was chasing another problem. That problem was leaks in intake/exhaust gaskets...I just left the "new' Tomco EGR valve on after repair.
At the same time I did this, I also pulled the Carter YFA (non feedback) carb and cleaned it up a bit. I also installed a new needle valve and seat. I set the float as best I could. The brass float (I am not the original owner here but have had this truck for 100M)was not leaking (no fuel inside) but had a dent on the side and the stem was twisted. I straightened it before reinstall.
I checked the PCV...rattles ok
I swapped out the cap, rotor, plugs and wires with known "good" used items that I had from a previous "tune up". more to come
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Junior User
Joined: Feb 2004
Posts: 87
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From: St.Paul, MN
Here's more (ran out of room)
It ran a bit better after this so drove to my cousin's (150 miles) on a warm (40) day (ran rich but I made it) and we checked the ignition on his SUN tester.Ok He's a good mechanic..checked my float adjustments..ok. Checked for vacuum leaks, found none. Electric choke module bad...did not replace, fixed hot air tube for convected heat and that is good enuf. Choke and fast idle work...open when warm.
Checked for vacuum leaks, found none. Improved on patches I had made to plastic vacuum lines. (cold so broke a couple)
Checked timing, 196M so advanced it.
Trap door in air snorkle was now staying closed so disconnected vacuum line at it and plugged line.
Still ran rough at low speed but started on minus 18 day and I drove home. Highway speed no miss or falter.
Fixes did not last...now getting worse again.
I will try to think of more.
It ran a bit better after this so drove to my cousin's (150 miles) on a warm (40) day (ran rich but I made it) and we checked the ignition on his SUN tester.Ok He's a good mechanic..checked my float adjustments..ok. Checked for vacuum leaks, found none. Electric choke module bad...did not replace, fixed hot air tube for convected heat and that is good enuf. Choke and fast idle work...open when warm.
Checked for vacuum leaks, found none. Improved on patches I had made to plastic vacuum lines. (cold so broke a couple)
Checked timing, 196M so advanced it.
Trap door in air snorkle was now staying closed so disconnected vacuum line at it and plugged line.
Still ran rough at low speed but started on minus 18 day and I drove home. Highway speed no miss or falter.
Fixes did not last...now getting worse again.
I will try to think of more.
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Junior User
Joined: Feb 2004
Posts: 87
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From: St.Paul, MN
Mixture is very rich, carbons up plugs.
I check and recheck the carb and egr nuts. tight.
Not related I am sure but fuel pump and filter are newer. Pump has about 40M on it, filter about 4-5m.
I have been told that the ICM either works or it doesn't so haven't swapped it out. I have another used one, condition unknown, if I ever have a no spark condition. Oh...and the ignition coil is not original. replaced it 4-5 years ago when chasing the other problem previously mentioned.
Cousin and I checked compression...#5 is lower than others but should be ok : From #1 150 160 160 150 110 155 I have a cold start noisy lifter...don't know which one but maybe #5 goes away on warm up.
Air pump still hooked up and turns. No "modifications" to existing pollution stuff ever.Always passed emissions testing when we had em (MN quit doing it)
I check and recheck the carb and egr nuts. tight.
Not related I am sure but fuel pump and filter are newer. Pump has about 40M on it, filter about 4-5m.
I have been told that the ICM either works or it doesn't so haven't swapped it out. I have another used one, condition unknown, if I ever have a no spark condition. Oh...and the ignition coil is not original. replaced it 4-5 years ago when chasing the other problem previously mentioned.
Cousin and I checked compression...#5 is lower than others but should be ok : From #1 150 160 160 150 110 155 I have a cold start noisy lifter...don't know which one but maybe #5 goes away on warm up.
Air pump still hooked up and turns. No "modifications" to existing pollution stuff ever.Always passed emissions testing when we had em (MN quit doing it)
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Joined: Sep 1999
Posts: 2,297
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From: Indiana
Ol Rudy
Have you manually held the choke plate open. Like twisted the choke cap to force the choke not to close at all? I have seen choke plate pull shut while drivng down the road, when the pull off is not working right. Its like it tries to reset the choke while you are driving.
I realize it could be a bear to get started. I would try that though. And drive it around for a while and see how it goes.
Have you manually held the choke plate open. Like twisted the choke cap to force the choke not to close at all? I have seen choke plate pull shut while drivng down the road, when the pull off is not working right. Its like it tries to reset the choke while you are driving.
I realize it could be a bear to get started. I would try that though. And drive it around for a while and see how it goes.
Senior User
Joined: Sep 2003
Posts: 497
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From: Houston TX
Mixture is very rich, carbons up plugs.
I check and recheck the carb and egr nuts. tight.
Have you taken the carb off the truck and checked for leaks?
IE: bad power valve diaphram, leaking bowl, etc..I was thinking you might look into your temp sensor. You say the carb is non feedback, but you say the air snorkle door is staying closed. That would normally mean the engine thinks it's cold. Might need a new sensor. Check CTAV system if it uses it. MK
I check and recheck the carb and egr nuts. tight.
Have you taken the carb off the truck and checked for leaks?
IE: bad power valve diaphram, leaking bowl, etc..I was thinking you might look into your temp sensor. You say the carb is non feedback, but you say the air snorkle door is staying closed. That would normally mean the engine thinks it's cold. Might need a new sensor. Check CTAV system if it uses it. MK
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Junior User
Joined: Feb 2004
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From: St.Paul, MN
Thanks....lots of detail on inline 6 forum .
I have had the carb off several times...adjusted and readjusted float...no power valve on Carter YFA. I cleaned, ckhecked for leaks
I do not know what the temp sensor looks like or where it would be. Unit has a smog pump, egr, pcv valve, brittle plastic vacuum lines...etc. Plus plastic one way vacuum connectosr on top and side of air cleaner.The one on top is for the snorkel....side has two plug in ubes...to plastic lines.
Give me a name for this temp sensor and I will look it up...may not exist yoyu know.
Oh...has electric choke (non working) and a throttle gizmo that is also electrical.
Today I went at it again...and may have it. More later
I have had the carb off several times...adjusted and readjusted float...no power valve on Carter YFA. I cleaned, ckhecked for leaks
I do not know what the temp sensor looks like or where it would be. Unit has a smog pump, egr, pcv valve, brittle plastic vacuum lines...etc. Plus plastic one way vacuum connectosr on top and side of air cleaner.The one on top is for the snorkel....side has two plug in ubes...to plastic lines.
Give me a name for this temp sensor and I will look it up...may not exist yoyu know.
Oh...has electric choke (non working) and a throttle gizmo that is also electrical.
Today I went at it again...and may have it. More later
Senior User
Joined: Sep 2003
Posts: 497
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From: Houston TX
The temp sensor if part of the CTAV system. "cold temperature activated vacuum". The temp switch is in the air cleaner. There is a latching relay, and a 3-way solenoid valve "vacuum switch" . It matches spark advance per temp. Selects carb spark port vacuum below 49f, and EGR vacuum when cold. A diagram is in the 1965-86 chiltons ford truck manual. MK
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Thread Starter
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Junior User
Joined: Feb 2004
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From: St.Paul, MN
Thanks...I have that book.
Also...the last carb check fixed it as far as fuel goes. NAPA had sold me the wrong kit...was for a YF carb not a YFA. Long story but here in St Paul Mpls Metro you can no longer call a NAPA store...any telephone number listed (by location) dials you into a central warehouse/boiler room. It's a mess....and by the way, if this arrangement comes to your town, protest . They are now pushing cheaper parts (not echlin/napa).and promise delivery next day to store cuz "nothing is in stock"...ha ha.
I put the old needle valve and seat back in, readjusted the float and bingo. Still chasing the vacuum pollution control stuff cuz of the hose breakage during cold. The snorkel tube door stays shut so temp valve is probably bad...I plugged line so door is open.
There is a throttle positioning sensor...push rod device, electrical, and it won't let the truck idle down...still driveable ...but fast. I WILL wrestle the balance to the ground...choke, fast idle, etc.
Also...the last carb check fixed it as far as fuel goes. NAPA had sold me the wrong kit...was for a YF carb not a YFA. Long story but here in St Paul Mpls Metro you can no longer call a NAPA store...any telephone number listed (by location) dials you into a central warehouse/boiler room. It's a mess....and by the way, if this arrangement comes to your town, protest . They are now pushing cheaper parts (not echlin/napa).and promise delivery next day to store cuz "nothing is in stock"...ha ha.
I put the old needle valve and seat back in, readjusted the float and bingo. Still chasing the vacuum pollution control stuff cuz of the hose breakage during cold. The snorkel tube door stays shut so temp valve is probably bad...I plugged line so door is open.
There is a throttle positioning sensor...push rod device, electrical, and it won't let the truck idle down...still driveable ...but fast. I WILL wrestle the balance to the ground...choke, fast idle, etc.
Last edited by Ol Rudy; Feb 11, 2004 at 03:45 PM.
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