FJ drives well for 10 minutes or so but once it gets hot it loses considerable power/acceleration in all gears. Cleaned the carburetor and replaced fuel filter (already has new plugs) but that didn’t do it. Any ideas?
Help with diagnosis - ‘79 FJ40 with 2F (1 Viewer)
- Thread starter dmcdon17
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
What’s the water temp when it stumbles and dies??? Sounds like a water pump or radiator issue…or even a stuck open exhaust flapper…,
Put some gas dryer in the tank and change the fuel filter again. Set the filter you take off in the sun for a few days - it will dry out and be good again. Paper elements don't let gas threw if wet with water.
Klooge in a $10 electric fuel pump and see it that fixes it.
Scrape the contacts inside the dizzy cap - aluminium oxide is an insulator.
See if your vacuum is good. Check the dizzy to see if it retards/advances properly. Got an idle cut off? Make sure it clicks when it get power - a jumper to by pass the ignition might help.
Klooge in a $10 electric fuel pump and see it that fixes it.
Scrape the contacts inside the dizzy cap - aluminium oxide is an insulator.
See if your vacuum is good. Check the dizzy to see if it retards/advances properly. Got an idle cut off? Make sure it clicks when it get power - a jumper to by pass the ignition might help.
Secondaries might be opening and staying open. Another issue can be the solenoid that shuts fuel off upon shut down.
Is this suddenly new or has it been coming on slowly? When did it get it's last good tune up? What's the timing set at? What do you mean by "cleaned the carburetor"? Took it apart and soaked it or sprayed some cleaner down it?
Smogged or not?
- Thread starter
- #6
It doesn’t die (although I usually just drive it home after) it just labors. It feels like driving with the parking brake on!
- Joined
- Apr 14, 2004
- Threads
- 1,447
- Messages
- 36,587
- Location
- 818-953-9230
- Website
- www.marksoffroad.net
Last time the valves were adjusted?
Hot valves may not be fully closing. This would definitely cause a drop in power. Unfortunately, with the high volatility of RFG, it’s also a very short run to a burned valve.
Hot valves may not be fully closing. This would definitely cause a drop in power. Unfortunately, with the high volatility of RFG, it’s also a very short run to a burned valve.
- Thread starter
- #8
This came out of nowhere. My mechanic gave it a tuneup in the spring. Sorry, I don’t know my way around an engine. The shop where I take it is pretty good and one of the mechanics has a few FJ’s, but the guys in this forum have such great advice I thought I would post and pass along any ideas.
- Thread starter
- #9
Thanks. This is what my mechanic just texted he is going to check on Monday. Appreciate the advice.Last time the valves were adjusted?
Hot valves may not be fully closing. This would definitely cause a drop in power. Unfortunately, with the high volatility of RFG, it’s also a very short run to a burned valve.
If the valves don’t fully close, there would be a ‘back fire’ associated, a popping under load. Could be fuel related as @charliemeyer007 suggests, but if it overheats you get into a fuel standoff….
With that said, what type of fuel, ethanol laced? And what is the ambient outside temperature? If so you could be suffering from a bit of vapor lock…..
Pictures would be nice…
With that said, what type of fuel, ethanol laced? And what is the ambient outside temperature? If so you could be suffering from a bit of vapor lock…..
Pictures would be nice…
- Thread starter
- #11
There’s not an actual backfire, but there is a little popping out of the exhaust, there is some rattling under the hood.
In terms of fuel, not sure about ethanol. I use regular (87) at shell or Exxon so I assume so.
Lastly, pretty mild here in NJ over the past few weeks. Cool evenings (50’s) and mild days (60-70s).
If you pull the choke, does it seem to improve any?
- Thread starter
- #13
Didn’t try that. Mechanic has it now. What would that tell me?
If pulling the choke helps it could indicate a vacuum leak. Also starting in 79, the emission computer controls the fuel cut solenoid. Sometimes pulling the choke will improve that. But typically, these are idle issues not loss of power in general.
The emission computer can get solder cracks at the connector and things start to happen with temperature changes. Not saying that is your problem but some stuff to check. You can hard wire the fuel cut solenoid to +12v to rule out the emission computer.
The times I have had this issue was water in the gas clogging the fuel filter and the inside of my distributor was corroded because the vent was not hooked up.
The emission computer can get solder cracks at the connector and things start to happen with temperature changes. Not saying that is your problem but some stuff to check. You can hard wire the fuel cut solenoid to +12v to rule out the emission computer.
The times I have had this issue was water in the gas clogging the fuel filter and the inside of my distributor was corroded because the vent was not hooked up.
Last edited:
