WHYDTYTT: What Have You Done To Your Truck Today?

[ArdWrknTrk]

http://forum.garysgaragemahal.com/file/n103070/F581F900-9FAE-42A4-88E8-A350B6A7A7F2.jpeg

"And here we see the Arizona burro in it's natural environment, doing what it does best."

Good job Jonathan!

That is incredibly tight.

I don't think even a front hitch would have helped me.

Yesterday my sister had come to town and wanted to meet up and go to a picnic.

We agreed on a time, but on my way she moved up the time and urgency.

So I went to pass a car ahead of me, and it seemed like I started to run out of gas. (this isn't too uncommon since my gauge doesn't work, I go by odometer)

But it didn't pick up switching tanks, and seemed I needed a lot of throttle to maintain speed.

Pulling away from the ramp it was really bad, but I was on a mission to get there.

My truck idles okay, but stumbles and has a very hard time gaining speed.

It seems almost like the cat is clogged (but not on all cylinders)

Today I dug into it thinking it was a fuel problem but the bowls are full, I have a good accelerator pump shot, and can't see any spill over. (plus this happens from a dead stop, where I know the bowls are full)

I checked over all the vacuum lines and pulled the spark plugs.

The plugs all look fine and pretty much the same.

No soot or oily deposits. (I gave them a lick of 400 grit, checked the gaps and replaced)

Checked the cap and rotor. Both okay. Same cleanup and replace...

I swapped my spare module and ohmed the wires.

My next step is going to have to be pulling the valve covers looking for a bent pushrod or wiped lobes.

Compression seems good. It doesn't spin over fast and none of the plugs are burnt or fouled.

The one thing I have done to the truck in the last week or so was change the oil....

I didn't use my regular diesel oil, but a 2 gallon jug of store brand.

But this cam has been in since the engine in March 2008.

Maybe it was just time? I don't know.

I don't even know what's wrong, yet. But hours of poking around without major disassembly have not given any obvious signs.

[Gary Lewis]

Yesterday my sister had come to town and wanted to meet up and go to a picnic.

We agreed on a time, but on my way she moved up the time and urgency.

So I went to pass a car ahead of me, and it seemed like I started to run out of gas. (this isn't too uncommon since my gauge doesn't work, I go by odometer)

But it didn't pick up switching tanks, and seemed I needed a lot of throttle to maintain speed.

Pulling away from the ramp it was really bad, but I was on a mission to get there.

My truck idles okay, but stumbles and has a very hard time gaining speed.

It seems almost like the cat is clogged (but not on all cylinders)

Today I dug into it thinking it was a fuel problem but the bowls are full, I have a good accelerator pump shot, and can't see any spill over. (plus this happens from a dead stop, where I know the bowls are full)

I checked over all the vacuum lines and pulled the spark plugs.

The plugs all look fine and pretty much the same.

No soot or oily deposits. (I gave them a lick of 400 grit, checked the gaps and replaced)

Checked the cap and rotor. Both okay. Same cleanup and replace...

I swapped my spare module and ohmed the wires.

My next step is going to have to be pulling the valve covers looking for a bent pushrod or wiped lobes.

Compression seems good. It doesn't spin over fast and none of the plugs are burnt or fouled.

The one thing I have done to the truck in the last week or so was change the oil....

I didn't use my regular diesel oil, but a 2 gallon jug of store brand.

But this cam has been in since the engine in March 2008.

Maybe it was just time? I don't know.

I don't even know what's wrong, yet. But hours of poking around without major disassembly have not given any obvious signs.

Bummer, Jim! I hope it turns out to be easy. Simple. But I don't know what that would be. You've done the first thing that came to my mind, the ignition module. What about the pickup in the dizzy?

[ArdWrknTrk]

Bummer, Jim! I hope it turns out to be easy. Simple. But I don't know what that would be. You've done the first thing that came to my mind, the ignition module. What about the pickup in the dizzy?

I checked the vacuum advance.

I should ohm out the pickup, but it doesn't make sense to me that idle is rock solid and once I get it up to speed it isn't missing.

Like I said acceleration is stumbling and glacial.

If I back off I can still feel what seems like a miss, and the exhaust note is 'off'

No backfire or spitting out the carb.

I could swap carbs, but it doesn't seem to me a fuel problem.

[Gary Lewis]

I checked the vacuum advance.

I should ohm out the pickup, but it doesn't make sense to me that idle is rock solid and once I get it up to speed it isn't missing.

Like I said acceleration is stumbling and glacial.

If I back off I can still feel what seems like a miss, and the exhaust note is 'off'

No backfire or spitting out the carb.

I could swap carbs, but it doesn't seem to me a fuel problem.

Speaking of fuel, how recently did you fill up?

A rock-solid idle doesn't seem to suggest a wiped cam. I can assure you that a bad cam WILL show up at idle - to the point that I thought the mirrors might come off if I didn't shift out of Drive to Neutral. And even then it was rough. But, I did have two bad cylinders back-to-back in the firing order.

Down on power sounds like something common to all cylinders, like ignition or fuel. Bad fuel.

[ArdWrknTrk]

Speaking of fuel, how recently did you fill up?

A rock-solid idle doesn't seem to suggest a wiped cam. I can assure you that a bad cam WILL show up at idle - to the point that I thought the mirrors might come off if I didn't shift out of Drive to Neutral. And even then it was rough. But, I did have two bad cylinders back-to-back in the firing order.

Down on power sounds like something common to all cylinders, like ignition or fuel. Bad fuel.

I failed to mention I cracked the front bowl loose to see if any water spilled out.

Lots of gas but no water, and no debris on the paper towel.

I hadn't put fuel in over 150 miles before this happened.

I always reset the odo on fill up and usually flip 160-165 miles.

I might have to pull the carb apart to look, but my fuel log makes that more complicated than it could be.

I wouldn't say idle is perfect, but it isn't low, and there's no sense it's going to stall until I open the throttle and try to apply load.

 

[Gary Lewis]

I failed to mention I cracked the front bowl loose to see if any water spilled out.

Lots of gas but no water, and no debris on the paper towel.

I hadn't put fuel in over 150 miles before this happened.

I always reset the odo on fill up and usually flip 160-165 miles.

I might have to pull the carb apart to look, but my fuel log makes that more complicated than it could be.

I wouldn't say idle is perfect, but it isn't low, and there's no sense it's going to stall until I open the throttle and try to apply load.

Ok, so bad fuel probably isn't the problem. And it idles ok, but doesn't have power. If there's no bucking, like the timing chain hasn't slipped or the ignition system is bad then I'm back to your idea about clogged exhaust.

I once packed a header muffler on a 750 K1 so tightly with stainless steel wool that it did NOT want to pull on the highway. Ran fine at lower RPM, but under load it would not wind nor pull. However, it was QUIET!

[Nothing Special]

I failed to mention I cracked the front bowl loose to see if any water spilled out.

Lots of gas but no water, and no debris on the paper towel.

I hadn't put fuel in over 150 miles before this happened.

I always reset the odo on fill up and usually flip 160-165 miles.

I might have to pull the carb apart to look, but my fuel log makes that more complicated than it could be.

I wouldn't say idle is perfect, but it isn't low, and there's no sense it's going to stall until I open the throttle and try to apply load.

I had something like that once with a Chevy 350 that turned out to be a bad fuel pump. It idled fine, but wouldn't make any power and barely kept running when the throttle was opened. That was a long time ago (in about 1984?) so I don't remember any more details.

[ArdWrknTrk]

I had something like that once with a Chevy 350 that turned out to be a bad fuel pump. It idled fine, but wouldn't make any power and barely kept running when the throttle was opened. That was a long time ago (in about 1984?) so I don't remember any more details.

Bob, I don't think it's the pump.

After dumping the front bowl I filled it through the vent, started it and immediately tried to move it.

The truck wouldn't take throttle.

My personal experience is that the truck will idle for almost three minutes before sputtering if I have the fuel line disconnected and plugged to the fuel pressure gauge.

I need to get a fresh filter, and I will check the pressure that way then.

Gary, one of the first things I did was walk around back and give the tailpipe a sniff for unburned fuel. (because I didn't understand the 'miss')

It's not rich and I'm not getting and popping or explosions like I would with a blown Powervalve or intermittent ignition.

My truck has no Cat, a huge fully welded only baffled school bus muffler and a 3" mandrel bent stainless tail pipe.

It seems to flow fine, with none of the joints blowing out.

This doesn't mean there can't be a clog wide open, but I can't be in the cab or under the hood holding the throttle, and around the back checking at the same time.

The exhaust note does sound flat. Like the engine is struggling.

It's almost three. I need to go back to sleep and stop stressing until there's daylight and I can do some more diagnosis.

 

[Gary Lewis]

Bob, I don't think it's the pump.

After dumping the front bowl I filled it through the vent, started it and immediately tried to move it.

The truck wouldn't take throttle.

My personal experience is that the truck will idle for almost three minutes before sputtering if I have the fuel line disconnected and plugged to the fuel pressure gauge.

I need to get a fresh filter, and I will check the pressure that way then.

Gary, one of the first things I did was walk around back and give the tailpipe a sniff for unburned fuel. (because I didn't understand the 'miss')

It's not rich and I'm not getting and popping or explosions like I would with a blown Powervalve or intermittent ignition.

My truck has no Cat, a huge fully welded only baffled school bus muffler and a 3" mandrel bent stainless tail pipe.

It seems to flow fine, with none of the joints blowing out.

This doesn't mean there can't be a clog wide open, but I can't be in the cab or under the hood holding the throttle, and around the back checking at the same time.

The exhaust note does sound flat. Like the engine is struggling.

It's almost three. I need to go back to sleep and stop stressing until there's daylight and I can do some more diagnosis.

Jim - Hope you got some sleep. And good luck finding it.

If the engine won't pull immediately after filling the bowl I'd agree it probably isn't the fuel pump or a hung up needle. But it still could be a plugged passage in the carb, something that was in the fuel and go past the filter. How hard is it to swap carbs?

And I agree it probably isn't a plugged exhaust given how large and open it is. So the "flat" sound may be a consequence of the way the engine is running rather than a plug.

Again, good luck!

[ArdWrknTrk]

Jim - Hope you got some sleep. And good luck finding it.

If the engine won't pull immediately after filling the bowl I'd agree it probably isn't the fuel pump or a hung up needle. But it still could be a plugged passage in the carb, something that was in the fuel and go past the filter. How hard is it to swap carbs?

And I agree it probably isn't a plugged exhaust given how large and open it is. So the "flat" sound may be a consequence of the way the engine is running rather than a plug.

Again, good luck!

I didn't 'sleep' well...

So far this morning I've checked the exhaust closer and don't think that's the problem.

I took my IR thermometer and noted no big differences in exhaust port temps (dead cylinder)

I used a long screwdriver to listen up and down both valve covers.

Nothing out of the ordinary.

I definitely need to dig into the carb. It does act like the idle circuit is fine but just off idle it struggles terribly.

Here's hoping I have a bit of fuel line and can get the 750 off without tearing the gasket, because I've got no way to get to an auto parts store.