HELP---Strange Engine Noise is very puzzling

[raythomas]

2 hours ago, Stoffregen Motorsports said:

You may have to rig up an in-line block or tee to test pressure, if there is no schrader valve (I can't believe that there wouldn't be one somewhere...)

 

Generally, the pump primes with key0on, but it will  not always cycle if sufficient pressure exists.  So turning the key on and off then on again, you may not hear it cycle, because it already has enough pressure.

 

Many EFI setups use a cold start injector. If this system uses one, then you may not see fuel spray from the main injectors on start up.

 

 

This fuel pump turns on each time you turn the key off and back on again. I can physically hear it pumping when I do that. I can turn on the key, hear the pump, turn off the key, then turn the key back on and it will pump again. I have done this as many as 5 times in a row and it always comes back on for about 5 seconds before it stops pumping. 

I don't think it has a schrader valve. Unless it's mounted on the TB somewhere. The lines come up the right side frame rail to the filter on the fenderwell and then across to the TB, then the return line goes from the TB back down the frame rail to the tank. I've worked on a Toyota once that had a cold start valve set-up. And I have yet to see anything like that on this truck. Going to borrow a gauge today, hope to test this evening, or tomorrow after work. 

 

Thanks

Ray

Edited October 1, 2023 by raythomas

[raythomas]

Okay, got the pressure checked this evening after work. And wouldn't you know it, its perfect. Right at factory setting of 36 psi.

I cranked it and the needle never moved the whole time it was running. I let it run until the engine was warm and then shut it off. 

Waited about 15 minutes and in those 15 minutes the needle on the gauge may have went down to 32 or 33 psi. After 15 minutes I turned the key forward, heard the pump come on and the needle on the gauge went right back to 36 psi. Cranked it over and the needle never moved. Truck started back up with 36 psi showing on the gauge. 
Whatever the problem is must be in the TB unit. Weird thing is, It started right back up after it had sat for 15 minutes. Any other time it would wind over and not start until I push the throttle to the floor. I turned it off and restarted it 3 times and it started right up each time. Just like it does when its cold. 

Any ideas now?

 

Thanks

Ray

[bilzbobaggins]

Did it set for those 15 minutes with the hood up?  

[raythomas]

1 minute ago, bilzbobaggins said:

Did it set for those 15 minutes with the hood up?  

 

It did, but it did the same thing the other night when it wouldn't start when hot. So don't think the hood up or down has a bearing on the problem.

Thanks
Ray

[bilzbobaggins]

1 minute ago, raythomas said:

 

It did, but it did the same thing the other night when it wouldn't start when hot. So don't think the hood up or down has a bearing on the problem.

Thanks
Ray

 

Dang.  Thought it might have been a heat soak issue of some sort.

[raythomas]

Let me rephrase that. I had the hood up the other night when the engine warmed up and the truck would not start then. That's why I don't think the hood being up or down has anything to do with it.

Thanks

Ray

[raythomas]

2 minutes ago, bilzbobaggins said:

 

Dang.  Thought it might have been a heat soak issue of some sort.

 

Thanks, But I'm afraid at this point I couldn't get "THAT" lucky .

 

Ray

[raythomas]

Some mentioned earlier about the temp sensor that talks to the ECU not the gauge in the dash. Is there a easy way to test that? Could that be a problem with hot starts? I'm having a hard time trying to figure out how something on the TB could be causing it. Seems like if it was the issue the truck wouldn't want to run period, hot or cold. I can't wait to see what you fellows have to say about all this so far. 

Thanks

Ray

[datzenmike]

When cold the temp sender tell the ECU so that a richer mixture is used during warm up, and the O₂ sensor is ignored. (open loop) When warmed up the mixture comes under control of the O₂ sensor (closed loop) and  reduced to stochiometric.

 

If not working the engine might remain in open or closed loop. If open it would still run, though rich, and if in open mode might be slightly harder to start when cold but would restart normally when warm.

[raythomas]

4 hours ago, datzenmike said:

harder to start when cold but would restart normally when warm.

 

So I'm gonna go out on a limb here and say the ECU temp sending sensor is probably working fine? Cause this truck starts fine when cold but is hard to start after warming up. Can't be TPS cause the idle seems fine, right at 850 rpm. And the throttle works great, not glitchy, or high idle problems.  What about that " heater plate" mounted under the TB next to the intake. It has a 2 wire connector going to it. Read somewhere that its only really needed for trucks in colder climates.

 

Thanks

Ray

[raythomas]

 

 

Found this after supper tonight. At least its a place to start.
Thanks
Ray

Edited October 8, 2023 by raythomas

[raythomas]

Crazy thing, I can't explain it but the hard start issue just disappeared. It just vanished. I have no idea how that happened. I did nothing to the truck except drove it about 10 miles killed it, let it sit for about 5 to 10 minutes and it started right up. Not a hicup. Goofy I know. At this point I'm not looking a gift horse in the mouth. I'm just enjoying having it to drive again.

 

thanks
Ray