12HT cold start issue

[CenTXFJ60]

i am not a diesel expert (mechanic) so need some assistance figuring out what’s wrong with my motor. I have a NOS motor that I transplanted into a fJ60 a few years ago (7K on the clock). Being in TX cold weather is not much of an issue. However it’s been in the high 30’s a few times this year and my motor acts like it’s 30 below. This morning it took over a minute to get it to run. And the black smoke is tremendous. Once it’s running and warmed up it runs great with no smoke. I did wire in a momentary switch through the relays for the glow screen. When I first put these in I was able to get 12V to the screen but that is no longer happening. I have a few other trucks with this motor and they fire right up in these conditions. Any thoughts, questions or suggestions are appreciated. Thanks.

 

[davegonz]

So you're not getting the full 12V at the screen? I'd check your connections from the battery to the relay.

 

[CenTXFJ60]

So you're not getting the full 12V at the screen? I'd check your connections from the battery to the relay.

Dave, I’m getting 12V to the solenoid but nothing past that. I can work around that but more concerned that it’s so sensitive to the cold. Our temps today are in the low 40’s and it won’t start. All other 12HT’s fire right up. And it seems to be worse than last year

 

[davegonz]

Fuel delivery issues?

 

[Mr Cimarron]

I’m with Dave that my guess would be something with fuel. Maybe the cold is letting air in the system or something? Direct injected diesels should be easier to start in cold than IDI diesels.

 

[CenTXFJ60]

I’m with Dave that my guess would be something with fuel. Maybe the cold is letting air in the system or something? Direct injected diesels should be easier to start in cold than IDI diesels.

That’s what my son said as well. So lacking experience with this aspect of the truck, would/could the temp alter the fuel delivery? @sami sent me a message on this as well and he suggested priming the motor prior to start. Gonna give that a try and see if there’s any improvement.

 

[Greg_B]

If it starts while hand priming look to replace the primer if you have not already. There is a Bosch number floating around here that is a nice replacement. Here is one.

My 13BT (and I know of a few others that have done the same) was getting harder to start in the temp zone just before the factory glow system would start kicking in (0C - 32F). A pump timing by @REDREEFER helped considerably. Also, make sure the valve set is current.

Here is the factory troubleshoot guide. While it appears your relay or solenoid is faulty (or the fuse on the grid heater side of the solenoid wiring is popped), the rest might help.

EM 22 - 25 in FSM RM012E covers the valve set and pump timing.

hth's
gb

 

[REDREEFER]

GB hit some good points and provided some great info.

Two things I would suggest right off the bat first being easier than the second to carry out so would check/ try the first first

First......
One common problem with the 12HT and others that can develop is the small 4mm hose that carries fuel back to the pump from the injector rail. I have found many that are dried out / heat soaked and are cracking at both ends and will allow air to be sucked into the fuel system when the vehicle sits for a period of time, over night. The factory clamps are not all that effective with the hard , cracked rubber as well.
With air in the system the 12HT does have a cranky time starting and clearing itself out in pretty much any temperature. I would suggest checking all points of possible air ingress into the fuel system as well, if it has a fuel/water separator on the frame you want to make sure that all is tight there as well. The fuel pick up / return tube assemblies in the tank can get rusty and cause this problem as well. Lastly if you notice any fuel wetness at the base of any of the delivery valves on the IP this will also cause a similar problem.

Second.....

Check pump timing, if it retarded, which many are, it will contribute to hard starts when cold.
Along with timing check, make sure that there is no slack in the accelerator cable and that the base idle is not set too low.

Cheers, hope this helps.

Rob

 

[Freewheel]

Black smoke is kind of odd for a hard start- my experience with glow system problems has always been unburned fuel, which is white.

Black smoke usually is about overfuelling. Not sure what my advice is, but that detail is a bit strange and you may want to think about why the truck may be overfuelling when cold?

 

[drenmaster]

Sorry to hijack your post @CenTXFJ60. I had some questions as well since the weather is actually colder in AZ this year. I went camping and it was about 25 degrees in the morning for a cold start. I turned the key for accessories and expected the glow screen light to come on. It never did, so I just turned the key and it took a maybe 5 seconds to crank and run. I would like to make sure the system is workign correctly but after reviewing my manual I am confused on checking it.

Is there a way to test the system? All i can find in my manual is troubleshooting. My vehicle is 24v.

 

[CenTXFJ60]

Sorry to hijack your post @CenTXFJ60. I had some questions as well since the weather is actually colder in AZ this year. I went camping and it was about 25 degrees in the morning for a cold start. I turned the key for accessories and expected the glow screen light to come on. It never did, so I just turned the key and it took a maybe 5 seconds to crank and run. I would like to make sure the system is workign correctly but after reviewing my manual I am confused on checking it.

Is there a way to test the system? All i can find in my manual is troubleshooting. My vehicle is 24v.

Not a problem Mark. If you find any of your relays are bad, hit me up as I have a few I can part with.

 

[Mr Cimarron]

When is the next barn day? A few people drinking beer may be able to figure it out.

 

[CenTXFJ60]

If it starts while hand priming look to replace the primer if you have not already. There is a Bosch number floating around here that is a nice replacement. Here is one.

My 13BT (and I know of a few others that have done the same) was getting harder to start in the temp zone just before the factory glow system would start kicking in (0C - 32F). A pump timing by @REDREEFER helped considerably. Also, make sure the valve set is current.

Here is the factory troubleshoot guide. While it appears your relay or solenoid is faulty (or the fuse on the grid heater side of the solenoid wiring is popped), the rest might help.

EM 22 - 25 in FSM RM012E covers the valve set and pump timing.

hth's
gb

View attachment 1865922 View attachment 1865923

GB, really appreciate the detail here. I will check the fuel rail to ensure flow. I did unscrew my fuel filter and diesel flowed freely. Also, I do need to buy the Bosch plunger as my son put that in his 60 and loves it. I did play with mine and it seems to be holding pressure. Checking the valve settings is a good idea. I have 7k on this motor and did an adjustment when it had a few hundred miles on it. Pump timing would be a new job for me. This motor is a NOS that sat for 30+ years before I put in in my 60 a couple years ago. We did a lot of baselining as many seals were dried out etc. never did consider the pump though. As I mentioned above, the truck has always ran great except for cold starts so I did not give it any consideration. Thanks again for your input. Jimmy

 

[CenTXFJ60]

When is the next barn day? A few people drinking beer may be able to figure it out.

Thursday is the only day I’m traveling this week Cim. Would love to have you stop by. And get Dave to come along

 

[CenTXFJ60]

GB hit some good points and provided some great info.

Two things I would suggest right off the bat first being easier than the second to carry out so would check/ try the first first

First......
One common problem with the 12HT and others that can develop is the small 4mm hose that carries fuel back to the pump from the injector rail. I have found many that are dried out / heat soaked and are cracking at both ends and will allow air to be sucked into the fuel system when the vehicle sits for a period of time, over night. The factory clamps are not all that effective with the hard , cracked rubber as well.
With air in the system the 12HT does have a cranky time starting and clearing itself out in pretty much any temperature. I would suggest checking all points of possible air ingress into the fuel system as well, if it has a fuel/water separator on the frame you want to make sure that all is tight there as well. The fuel pick up / return tube assemblies in the tank can get rusty and cause this problem as well. Lastly if you notice any fuel wetness at the base of any of the delivery valves on the IP this will also cause a similar problem.

Second.....

Check pump timing, if it retarded, which many are, it will contribute to hard starts when cold.
Along with timing check, make sure that there is no slack in the accelerator cable and that the base idle is not set too low.

Cheers, hope this helps.

Rob

Rob, you and GB mentioned the timing. I will read up on how to check that. As for the hoses I will check all connections. I built this truck from the ground up and have had a more than a handful of thinks like this creep up. Good suggestion and much appreciated

 

[Mr Cimarron]

I put the Bosch plunger on my BJ and reordered another for my spare 3B off Amazon from the same link a year later and got a different one. Same part number.
First one looked like this, which I prefer. Second one was like the second photo which is more like the original Toyota version.

 

[CenTXFJ60]

Ok. I googled how to upload videos to YouTube and think I’ve figured it out. Gonna post some here and get yalls feedback

 

[davegonz]

Love the grunt sound from a 12HT!

 

[CenTXFJ60]

Another video after I ran it for a few minutes.

 

[CenTXFJ60]

Warm start showing puff of black smoke. I’m about to upload the cold start video showing how it won’t fire.