‘94 80 runs fine but lately bogging down (1 Viewer)

[auttiman]

when I push the gas peddle. I had to shut it off on the trail last night for a few minutes then start it back up and continue riding. Had to do this twice before I got it out of the woods and back home (the woods I was riding in are adjacent to my property.)

Any advice would be greatly appreciated.

 

[auttiman]

when I push the gas peddle. I had to shut it off on the trail last night for a few minutes then start it back up and continue riding. Had to do this twice before I got it out of the woods and back home (the woods I was riding in are adjacent to my property.)

Any advice would be greatly appreciated.

Bump. Where is the fuel filter located? Could this be what’s wrong?

 

[GSTMike]

Bump. Where is the fuel filter located? Could this be what’s wrong?

Look from the drivers side below the intake manifold, black canister with a banjo line into either end of it

 

[BILT4ME]

when I push the gas peddle. I had to shut it off on the trail last night for a few minutes then start it back up and continue riding. Had to do this twice before I got it out of the woods and back home (the woods I was riding in are adjacent to my property.)

Any advice would be greatly appreciated.

This is a REALLY vague statement. We cannot help you unless you give us more information.

1) How many miles on the truck
2) Does it sputter, miss or feel rough running when it does this?
3) Is it at low RPM or high RPM when you do this?
4) When was the last time any preventive maintenance was done?
5) What PM was done?
6) Was the engine hot or cold when this occurred?
7) Have you pulled any engine codes to determine if there is an issue there?
8) Have you changed your air filter?
9) How much fuel was in the tank?
10) What is your level of automotive experience so we can properly gear our answers to your understanding.
11) Is it your intent to do your own work or to pay someone else to work on it for you?
12) When you shut it off, how well did it restart?
13) What was the engine temperature when it started doing this?
14) Have you checked your coolant levels before or since?
15) What does your engine oil look like?

Otherwise, you'll get answers anywhere from:

Don't worry about it, just drive it.
to
You blew the head gasket. Looks like you're in for about $10,000 in repairs.

Maybe you need more air in the tires.

 

[auttiman]

This is a REALLY vague statement. We cannot help you unless you give us more information.

1) How many miles on the truck
2) Does it sputter, miss or feel rough running when it does this?
3) Is it at low RPM or high RPM when you do this?
4) When was the last time any preventive maintenance was done?
5) What PM was done?
6) Was the engine hot or cold when this occurred?
7) Have you pulled any engine codes to determine if there is an issue there?
8) Have you changed your air filter?
9) How much fuel was in the tank?
10) What is your level of automotive experience so we can properly gear our answers to your understanding.
11) Is it your intent to do your own work or to pay someone else to work on it for you?
12) When you shut it off, how well did it restart?
13) What was the engine temperature when it started doing this?
14) Have you checked your coolant levels before or since?
15) What does your engine oil look like?

Otherwise, you'll get answers anywhere from:

Don't worry about it, just drive it.
to
You blew the head gasket. Looks like you're in for about $10,000 in repairs.

Maybe you need more air in the tires.

-I first noticed it at high rpm last week while pulling a trailer up an incline so definitely at high rpm under load. It gets worse as it warms up but shutting it down for a few minutes enables it to run normally (not skipping) for a few minutes, then it starts again so I’m not thinking it has anything to do with engine temp. It gets so bad that touching the accelerator Boggs it down immediately so it has this problem at both high and low rpm. I was forced to put it in low range and let it idle home.
-Mileage is around 190k.
-Changed the oil when I got it and put a new tranny cooler on it. Other than that, I’m not aware of any other PM although the front axles look to be in excellent shape. Pretty sure they’ve been serviced within the past couple of years.
-Air filter looked fine last time the Toyota dealer changed the oil.
-Fuel level was half full.
-I’m a car wholesale dealer and know a good bit about auto repairs/problems.
Being in the car business, I’ve got shade tree mechanics sitting on go for most repairs. But I can do a lot of small things. Recently changed my starter, for example. Also dropped the tank in my Jeep and changed the sending unit. Swapped leaf springs on the same jeep.
-It restarts with no problem and runs smoothly at idle.
-I haven’t checked codes. I’ve got OBII scanner but this is pre OBII.
-Engine temp was low (normal for cold weather.)
-Coolant levels are normal.
-Engine oil is fine and at the proper level.

I’m thinking it’s a fuel blockage somewhere (in-tank filter or fuel filter in the engine bay.)
My main reason for asking this board the question is to learn if there are other common problems that that would cause this skipping/bogging.
I know I’ve read where some eliminate their EGR, system. I have no idea if EGR is related to my problems, though.

Again, thanks for any and all suggestions.

 

[BILT4ME]

Based on your description of how the symptoms manifested, yes, I would agree is could be fuel filter under the intake manifold or fuel sock inside the tank. High RPM then bogging or missing, then running fine at idle COULD be a clogged fuel system or a weak pump.

You can get a fuel pressure gauge and insert it inline and run the truck at high RPM to watch the fuel pressure changes if any. Realize that the fuel pump changes speed based on temperature sender input making the truck go from open loop to closed loop based on temp.

The fuel sock in the tank is the first and easiest to get to. Lift the rear seats and pull back the carpet and you'll see an access cover to get directly to the fuel pump. Relieve the pressure (pull the fuel pump fuse, start and run the truck until it dies), then remove the high pressure line and the return line, then the screws and you can lift out the pump and fuel sock.

You may want to buy a Toyota fuel sock replacement kit before you go there. The fuel pumps do not go out often, but at 190K you may want to change it "while you're in there". Use a Denso or Toyota pump.

The fuel filter under the intake is a huge pain to get to and swap. Some cussing involved. Look it up in a FSM or on this forum for tips. I have not done mine so I do not have first-hand experience to impart.

There are others that can chime in now as well to offer other possibilities.

 

[auttiman]

Based on your description of how the symptoms manifested, yes, I would agree is could be fuel filter under the intake manifold or fuel sock inside the tank. High RPM then bogging or missing, then running fine at idle COULD be a clogged fuel system or a weak pump.

You can get a fuel pressure gauge and insert it inline and run the truck at high RPM to watch the fuel pressure changes if any. Realize that the fuel pump changes speed based on temperature sender input making the truck go from open loop to closed loop based on temp.

The fuel sock in the tank is the first and easiest to get to. Lift the rear seats and pull back the carpet and you'll see an access cover to get directly to the fuel pump. Relieve the pressure (pull the fuel pump fuse, start and run the truck until it dies), then remove the high pressure line and the return line, then the screws and you can lift out the pump and fuel sock.

You may want to buy a Toyota fuel sock replacement kit before you go there. The fuel pumps do not go out often, but at 190K you may want to change it "while you're in there". Use a Denso or Toyota pump.

The fuel filter under the intake is a huge pain to get to and swap. Some cussing involved. Look it up in a FSM or on this forum for tips. I have not done mine so I do not have first-hand experience to impart.

There are others that can chime in now as well to offer other possibilities.

Thanks. That’s an in-depth answer and I genuinely appreciate it. I’m with you on the filter/sock in the tank. I can see it running long enough to suck a bunch of scum into it and causing blockage. Also, when I got it back in the spring, it had been sitting in a tow yard for a couple of years. I got it running and noticed the fuel gauge wasn’t working. Then, after putting premium non ethanol gas in it for a couple of tanks, the gauge started working. I’m thinking the gunk in the tank had “gummy bear’d” the gauge in place and the good gas finally freed it. Anyway, wouldn’t hurt to pull that pump and clean out the tank - as best as I can.

 

[BILT4ME]

Thanks. That’s an in-depth answer and I genuinely appreciate it. I’m with you on the filter/sock in the tank. I can see it running long enough to suck a bunch of scum into it and causing blockage. Also, when I got it back in the spring, it had been sitting in a tow yard for a couple of years. I got it running and noticed the fuel gauge wasn’t working. Then, after putting premium non ethanol gas in it for a couple of tanks, the gauge started working. I’m thinking the gunk in the tank had “gummy bear’d” the gauge in place and the good gas finally freed it. Anyway, wouldn’t hurt to pull that pump and clean out the tank - as best as I can.

These tanks do have a drain on them to get rid of the bad stuff in there if needed.

Also, PB Blast the connecting bolts on the straps that hold up the tank if you're going to consider dropping the tank for a cleaning. Do that a few times for a week or two prior to dropping the tank. Also consider replacing the high pressure hose while you have the tank out. Also consider changing the charcoal vapor canister using the VC-120 unit (search here for it) and Do NOT coat the inside of the tank.

If it's rusty, get a used tank. @slow95z or @arcteryx can help you with that if needed.

 

[slow95z]

I have several used tanks in stock that I might even be able to ship before Christmas if needed.

 

[auttiman]

I have several used tanks in stock that I might even be able to ship before Christmas if needed.

The tank itself doesn’t seem to need replacing. I have no rust so I’m thinking it my simply need cleaning the gunk out.

 

[auttiman]

These tanks do have a drain on them to get rid of the bad stuff in there if needed.

Also, PB Blast the connecting bolts on the straps that hold up the tank if you're going to consider dropping the tank for a cleaning. Do that a few times for a week or two prior to dropping the tank. Also consider replacing the high pressure hose while you have the tank out. Also consider changing the charcoal vapor canister using the VC-120 unit (search here for it) and Do NOT coat the inside of the tank.

If it's rusty, get a used tank. @slow95z or @arcteryx can help you with that if needed.

Update. So I finally got around to getting my mechanic to check it out. Before he loosened the fuel line I warned him to take the suggested steps to relieve fuel pressure. He had an old shirt nearby but insisted on unbolting it the way it sat so he could see if it had pressure. Well, it had none. No pressure in the line whatsoever. He thinks that means the pump is failing. Does this sound right?

 

[Tools R Us]

The most common cause of loaded miss, power problems, is the main engine harness rubbing on the EGR pipe. It's an easy check, there was a clip to hold it in place that fails with age, if this is the case, use a couple of zip-ties to secure the harness and see if that solves the problem.

 

[auttiman]

The most common cause of loaded miss, power problems, is the main engine harness rubbing on the EGR pipe. It's an easy check, there was a clip to hold it in place that fails with age, if this is the case, use a couple of zip-ties to secure the harness and see if that solves the problem.

View attachment 1885017

THANKS!

I’ll check that out!

 

[fz1boxer]

how long did the truck sit before he loosened the fuel lines?
pull the lines off the charcoal canister,vent any pressure off the gas tank drive around and see if the problem comes back.
i woud drain the fuel tank(easy) and see what kind of crap comes out,if you get a lot, then attack the fuel pump and sock next(easy),do the fuel filter last(cuss words).
when i did my fuel filter i cut it open and it was fuel of black stuff,ran better once i got it replaced but did not exhibit the signs yours does.
if you don't see any improvement go to the fuel pressure regulator$$

 

[BILT4ME]

Update. So I finally got around to getting my mechanic to check it out. Before he loosened the fuel line I warned him to take the suggested steps to relieve fuel pressure. He had an old shirt nearby but insisted on unbolting it the way it sat so he could see if it had pressure. Well, it had none. No pressure in the line whatsoever. He thinks that means the pump is failing. Does this sound right?

No pressure in the line can also mean the injectors are weak and allow the fuel to dribble out over time. Depending on how long the truck sat after running to the time he pulled the line, all the pressure and fuel COULD have dribbled out the injectors or worked it's way backwards through a check valve in the fuel line.

Get it running first, then worry about whether or not the injectors are leaking.

 

[Tools R Us]

No pressure in the line can also mean the injectors are weak and allow the fuel to dribble out over time. Depending on how long the truck sat after running to the time he pulled the line, all the pressure and fuel COULD have dribbled out the injectors or worked it's way backwards through a check valve in the fuel line.

Get it running first, then worry about whether or not the injectors are leaking.

But, that would cause a slight starting delay, extended crank before firing, not running/loaded power loss.

 

[BILT4ME]

But, that would cause a slight starting delay, extended crank before firing, not running/loaded power loss.

Agreed, it COULD.

Depending on the severity of the leak down and if it is ONE injector VS multiple, may create harder starting issues or cold hard starts, but warm starts OK.

Not enough detail here for full diagnosis.

 

[auttiman]

Agreed, it COULD.

Depending on the severity of the leak down and if it is ONE injector VS multiple, may create harder starting issues or cold hard starts, but warm starts OK.

Not enough detail here for full diagnosis.

The 80 had been parked less than 30 minutes. After he bolted the fuel line back on it fired right up (less than 3 seconds) same as it always does.

 

[auttiman]

or worked it's way backwards through a check valve in the fuel line.

Where is this check valve located?

 

[BILT4ME]

Where is this check valve located?

I'm not sure if it is part of the fuel pump or what......

I do not see it listed as a separate item, however, it states in the manual to bleed down the fuel pressure before servicing, so there must be one SOMEPLACE.

@Tools R Us : Do you have an answer?