bogging/difficult start (1 Viewer)

A62

Joined
Oct 4, 2018
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38
Location
Montana
Hi, everyone.
This is an issue I've struggled with for some time and have never gotten to the bottom of. It can be intermittent and hard to trace.
But recently I discovered a few things. The back story is: my rig, an 88 fj62, has been intermittently difficult to start, and/or, after starting will bog down suddenly once it's run for some time. When this occurs I usually can't go over 1500 rpms, but under that seems ok.

Once the rig sits for a while, the problem seems to go away unless I run it for an extended period--I've noticed around 60 miles of continuous driving will bring about the bogging issue.
Last year I changed the fuel filter, checked the MAF, checked for vacuum leaks, changed distributor cap (was thinking moisture) and even took it in to have it looked at, but the problem never presented itself to the mechanics, so they were baffled.

More recently, I've discovered that I can remedy the starting issue by venting the gas cap. A lot of pressure seems to be building in the gas tank, so much so I can here it gurgle down once I open the cap. So this takes care of the starting problem, but still, after running for a bit the bogging sometimes happens. Interestingly, too, weather seems to be a factor--another sign of pressure buildup, perhaps?

Clearly, I'm not much of a mechanic, so I thought I'd throw this one out there to get some feedback. Could it be as easy as replacing the cap? I've heard they can be problematic. Clogged fuel line? Fuel pump? I have a new fuel pressure regulator I've never put in, too.

Forgot to mention one important point! I pulled the codes and got 25 and 26: air/fuel ratio rich and lean.

Any thoughts would be appreciated. Even if it's "read the FSM!" which I have. I am a Land Cruiser owner after all. No place for sensitive or thin skinned people!
Thanks!
 
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Joined
Nov 25, 2014
Messages
486
Location
Western victoria Australia
Does the bogging problem go away if you loosen the fuel cap, leave it loose, [stop pressure building up temporarily] and take a long drive?
The fuel pressure regulator. Is that like an accumulator? Car will be hard to start if that's on the blink. def replace that,
 
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Seth S

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Jan 4, 2011
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4,137
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Vermont
the fuel pressure regulator is a little spring loaded valve or diaphragm on the end of the fuel rail. When the fuel pressure gets high enough the regulator opens and let’s fuel flow back to the tank. When the pressure drops it closes and let’s pressure in the rail build again. The 3FE EFI is designed around a specific pressure range. Pressure too high or to low will result in running problems. Best way to check the regulator is put a fuel pressure gage on the fuel line and watch the pressure. Drive it if you can and see if there is a pressure issue when your problem pops up.
 

A62

Joined
Oct 4, 2018
Messages
38
Location
Montana
Does the bogging problem go away if you loosen the fuel cap, leave it loose, [stop pressure building up temporarily] and take a long drive?
The fuel pressure regulator. Is that like an accumulator? Car will be hard to start if that's on the blink. def replace that,
Loosening the cap usually helps the starting issue only. In other words, if it's having problems starting and I loosen the cap, it's almost guaranteed to start--at least so far. A couple of weeks ago it bogged down suddenly on the freeway. I pulled over and tried venting the cap. Not much vapor vented out and it continued to run poorly for a few miles, but then recovered. So it's hard to say if that took care of it in the moment.
I haven't tried simply running with a loosened cap, but it seems to me that the cap is a long shot and more of a symptom to another problem. Just a hunch, though.
Thanks
 

A62

Joined
Oct 4, 2018
Messages
38
Location
Montana
Hi, Have you pulled the gas tank and changed the filter sock in the tank ? How old is the fuel pump ? Mike
Pump's maybe ten years old. I was hoping not to drop the tank right off the bat. But may not have a choice.
 
Joined
Apr 18, 2020
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Location
Sabah,Malaysia
Treatments on cleaning the injectors and general fuel lines..it flushes all the deposits and air out. I do mine once every year and it makes heaps of difference on performance and efficiency :)
 

A62

Joined
Oct 4, 2018
Messages
38
Location
Montana
Treatments on cleaning the injectors and general fuel lines..it flushes all the deposits and air out. I do mine once every year and it makes heaps of difference on performance and efficiency :)
Ah, got it. Thanks.
 

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