Struggling with my fj62 12ht. Fixed! Thanks for all the help! (1 Viewer)

[ClintOK]

so I bought a fj62 with what looks like a really clean 12ht conversion in it. Brought it home about 3 weeks ago and it ran great. Now I'm having trouble with it. If I start it and let it idle it will run fine. If I rev it up to 2000-2500 it runs great but if I try to drive it it will bog down and die after about 1/2 a mile. This all started a couple nights ago when I took my kids for a ride in the truck and it started struggling to run about 5 miles from home. It sputtered and died and I had to have my wife come with the f-250 and a tow rope to get it home. Since then I have changed the fuel filter, blown the lines out from the lift pump back to the tank with compressed air and looked all over the fuel lines for leaks with everything looking fine. I can get the truck to start and run if I crack the line coming from the fuel filter and use the priming pump to push air out of the lines until fuel runs out without bubbles. It will then start like always and run at idle just fine but when I drive it it will go about 1/2 to 1 mile and it bogs down and dies. I can then again bleed the lines and it will start and get me home but will be sputtering and dying by the time I get there. My question to you guys is should I try to find a replacement lift pump? Very unlikely that I will find one. Send injection pump to be repaired? Probably outside my skill set to remove it! Or maybe try to rig up a in-line fuel pump? Which one and will that even work? I'm very frustrated because I probably spent too much on a truck that is unreliable! Very frustrated!!

 

[dmjay]

Hi mate, i would try a new primer pump first. Perhaps replace some fuel lines as well. You have air getting in for sure.

 

[ClintOK]

Hi mate, i would try a new primer pump first. Perhaps replace some fuel lines as well. You have air getting in for sure.[/QUOTEthank you, I just ordered the Bosch replacement from amazon. I'll give it a try and see if that fixes it.

 

[roscoFJ73]

You need to check all the ends of the rubber fuel lines. Splitting lets air in. I doubt its anything to do with lift pumps. You could also add a length of clear hose temporarily before the fuel filters and see if the air is coming from before the filter.

Note When air gets in, it doesn't usually leak diesel unless its really bad.

The gauze on the fuel pick up sometimes gets clogged. And sometime the fuel pick up rusts around its base and lets air in, but this is usually only a problem where the roads are salted in winter.

Another way of to help diagnose things is to add a temporary fuel tank in the engine bay and see if that makes a difference. It would confirm if the lift pump is working as long as the fuel tank wasn't higher than the lift pump.
But I am laying my bets on air like it is 98% of the time

 

[gerg]

Sounds a lot like a fuel filter or the pick up in the tank is clogged. The separate fuel tank I've done and it gives you an immediate answer. You have to start eliminating possibilities. Start from the tank back. It a matter of a jerry can and a section of hose to the lift pump.

 

[ClintOK]

Sounds a lot like a fuel filter or the pick up in the tank is clogged. The separate fuel tank I've done and it gives you an immediate answer. You have to start eliminating possibilities. Start from the tank back. It a matter of a jerry can and a section of hose to the lift pump.

Sounds good, I will give the temp fuel tank a try tomorrow. Thanks

 

[ClintOK]

So the truck is still running like crap. I tried running it off of a jug of diesel directly into the lift pump and it idled all of the diesel away. This doesn't prove anything because it doesn't bog down and die until I drive it. I blew the lines out back to the tank and I could hear diesel bubbling in the tank but I couldn't find any leaks. I unhooked and tightened or checked each connection between the tank and the lift pump except the ones on top of the tank. I guess the next step is to drop the tank and check the hoses going into and out of it. After purging the lines with air back to the tank I hooked the lines back up and it will drive a short distance and then bog down and die. Is there any sensor or computer control module that I can try to mess with? I'm at a loss and don't know what else to do. I'll change out the hand prime pump but I honestly don't think that is the issue.

 

[Freewheel]

Is the fuel tank venting properly? Whenever I hear of a problem that happens after a time of higher throttle activity- I wonder whether the fuel tank is developing vacuum... The diesel engines have a very complex venting system and if yours is a conversion, maybe they cut some corners on it. For the heck of it try driving without the fuel cap on. (don't try this with a full tank of fuel...)

 

[gerg]

I took the rubber seal off of my tank cap because It was developing suction as the tank emptied. My suggestion of a separate fuel can was specifically for you to drive it. Use a long hose and put it on the passanger floor or belt that sucker in good. Tape a bolt to the end of the hose so it sinks and use a large can and full it only half full will lessen the chance of spilling. When I did this to a friend's truck he just bought it took like 5 min and we did it in the pouring rain on the side of the road. Got him home.

 

[roscoFJ73]

I tried running it off of a jug of diesel directly into the lift pump and it idled all of the diesel away. This doesn't prove anything because it doesn't bog down and die until I drive it

I meant to have a small container of diesel wired to hold it down and a rag or something to stop it slopping out. 2-3 litres would be plenty. Then it could be driven at road speed.
I also mentioned the clear piece of hose running to the filter back to where the fuel enters the engine bay. You will know if their is an air leak further back. Like this.

 

[dousty]

12HT priming plunger can allow air in. Is it pushed in and screwed down? Those plungers are common amongst Toyota diesels of that era so really aren't that hard to obtain.

 

[VX 12HT]

trying to think of something different would not be the butterfly valve for the vacuum shutdown mucking up would it ???

 

[roscoFJ73]

12HT priming plunger can allow air in. Is it pushed in and screwed down? Those plungers are common amongst Toyota diesels of that era so really aren't that hard to obtain.

I think you could use the Bosch plunger that the Mercedes use, only $30 on ebay.

 

[ClintOK]

trying to think of something different would not be the butterfly valve for the vacuum shutdown mucking up would it ???

This is what I'm thinking it is. I can't find a leak in the fuel lines anywhere and I've tightened and checked everywhere I can think to check. I have the Bosch pump coming so I will change that out and see if it helps. I am seriously starting to think it's a vacuum issue. Where is this valve and how do I check its function? It only acts up when I'm driving it at near highway speeds and then it will burble and buck when it's trying to accelerate in 4th gear. Then it will lose all power and die.

 

[remy]

There is a small filter inside the primer pump banjo bolt. That one is clogged.

 

[ClintOK]

There is a small filter inside the primer pump banjo bolt. That one is clogged.

Awesome! I'll give that a look. Do you know if it is coming into the pump or out of the pump?

 

[ClintOK]

There is a small filter inside the primer pump banjo bolt. That one is clogged.

Remy, where do I send the bottle of whisky? You are the man! I pulled that filter and it was completely clogged with gunk. Cleaned it out and blew the lift pump out front to back with air and it ran down the road better than it ever has since I've owned it. I cant tell you how much I appreciate your help and all the help from the people on this forum!

 

[VX 12HT]

excellent news glad you got it sorted...

 

[gerg]

Glad to hear it's unclogged. Might be a good time to drain your fuel tank as you might have some stuff hiding in there.

 

[ClintOK]

Glad to hear it's unclogged. Might be a good time to drain your fuel tank as you might have some stuff hiding in there.

When I bought the truck the guy said he dropped the tank and cleaned it all out with tank cleaner so it should be good to go now. I think this crud in the filter was the last of it. Hopefully I won't have any more issues.