Hard warm starts

[mitchsc0tt0]

Hey guys I am having a strange issue. Truck starts great when cold quick blip of the button and it fires. When warm after a short drive if it sits for a few min and I come back it takes a few cranks to get it to fire. Any ideas? It's completely stock minus fdc bypass.

 

[Gypsyman]

Did this just start? Getting progressively worse? Always been this way? Are you running straight diesel or alternative fuels?

First though would be poor tank venting creating a vacuum after some run time. You can check this by slowly cracking the fuel fill and seeing if you hear it hiss. You could also try making a run with the cap loose to avoid any possible vacuum situation and see if the hot restart problem goes away.

 

[mitchsc0tt0]

It just started over the past few times I've had it out. I haven't noticed it get worse as of yet. I mostly run diesel but do mix a bit of wmo filtered and blended with diesel off and on. I'll go ahead and see if the cap fixes anything next time I go out.

Did this just start? Getting progressively worse? Always been this way? Are you running straight diesel or alternative fuels?

First though would be poor tank venting creating a vacuum after some run time. You can check this by slowly cracking the fuel fill and seeing if you hear it hiss. You could also try making a run with the cap loose to avoid any possible vacuum situation and see if the hot restart problem goes away.

 

[Mullaney]

It just started over the past few times I've had it out. I haven't noticed it get worse as of yet. I mostly run diesel but do mix a bit of wmo filtered and blended with diesel off and on. I'll go ahead and see if the cap fixes anything next time I go out.

.
First and Cheapest thing to look at would be fuel filters. Even if they were changed recently, maybe "something you fed your truck" has gummed up the filters?

 

[Gypsyman]

Usually a rapid onset problem indicates a change or some type of failure. As Mullaney stated above, possibly as simple as filters. Always chase the simple solutions first.

Could even be a lift pump that gets weaker as it heats up. I have seen that. Any changes in smoke output or color?

 

[mitchsc0tt0]

The filters I just changed less then a month ago but agreed I will give them a check. Its weird though because I would think if it was filters or a weak lift pump wouldn't it have more problems when cold? The smoke output at idle is pretty smoky but clears up when up to speed. And agreed with the failure aspect. I was digging around the other day and can't really see anything that points to an issue (at least externally). My first thought was fuel leak somewhere but not seeing anything visible on that route.

 

[ToddJK]

That is weird. Was there any vacuum pressure in the fuel tank?
I had some leaks and most of them causes air to get into the system, so it would start but then within 10-15 seconds, there would be a hard stall, where the air pocket was.

 

[JasonS]

Difficult hot start on the PSB injection pump is often attributed to a worn plunger in the hydraulic head.

 

[mitchsc0tt0]

Ugh that's not what I was hoping for ...one thing I did notice is if I leave the pump on for like 10 seconds or so it does seem to start right up. Still think it's plunger or could an air leak cause it? But idk how I could test for an air leak?

Difficult hot start on the PSB injection pump is often attributed to a worn plunger in the hydraulic head.

 

[ToddJK]

Ugh that's not what I was hoping for ...one thing I did notice is if I leave the pump on for like 10 seconds or so it does seem to start right up. Still think it's plunger or could an air leak cause it? But idk how I could test for an air leak?

I doubt it's an air leak. It'll either take a lot of cranking to start or it will start up like normal and have a hard stall shortly after. There may be more things that could happen if there was an air leak, but that's been my experience with two different deuces.
You could simply crack the bleeder valve open above the secondary filters and let some air in or drain some fuel from the primary and secondary filters, not much but 5 seconds worth of fuel while that bleeder valve is open. This will let air in. Try to start it, it should start but it should stall once that air pocket hits the IP.
Honestly that doesn't sound like the issue, if there's an air leak, it will happen every time, cold or hot. I think the plunger may be suspect, but it's inevitable, parts in the IP will wear over time.
If you can't get the parts to rebuild the HH, from my understanding, the Chinese made HH which was talked about here on other threads seem to work pretty well and have a better system in which that button doesn't fall off like it does in the OEM HH if I understand that correctly. Last I saw those were around the $500 range.

 

[mitchsc0tt0]

Thanks for that info great write up!

I doubt it's an air leak. It'll either take a lot of cranking to start or it will start up like normal and have a hard stall shortly after. There may be more things that could happen if there was an air leak, but that's been my experience with two different deuces.
You could simply crack the bleeder valve open above the secondary filters and let some air in or drain some fuel from the primary and secondary filters, not much but 5 seconds worth of fuel while that bleeder valve is open. This will let air in. Try to start it, it should start but it should stall once that air pocket hits the IP.
Honestly that doesn't sound like the issue, if there's an air leak, it will happen every time, cold or hot. I think the plunger may be suspect, but it's inevitable, parts in the IP will wear over time.
If you can't get the parts to rebuild the HH, from my understanding, the Chinese made HH which was talked about here on other threads seem to work pretty well and have a better system in which that button doesn't fall off like it does in the OEM HH if I understand that correctly. Last I saw those were around the $500 range.

 

[ToddJK]

I didn't think to ask, but does this happen when you run straight diesel as well? I know sometimes fuel mixtures can be a little more difficult to start up. I've noticed that myself, straight diesel or a mixture high in jet fuel, my truck will start up with just a tap of the starter button, but in cases where I'm running a lot more wmo, it needs to crank more before she fires over, but it does this hot or cold, just less cranking when she's hot.

 

[mitchsc0tt0]

On regular diesel right now and it does it. I would figure if it was bad fuel it would have more issue when cold. I am having the opposite starts great when cold takes about 3 blips of the starter switch when warm.

I didn't think to ask, but does this happen when you run straight diesel as well? I know sometimes fuel mixtures can be a little more difficult to start up. I've noticed that myself, straight diesel or a mixture high in jet fuel, my truck will start up with just a tap of the starter button, but in cases where I'm running a lot more wmo, it needs to crank more before she fires over, but it does this hot or cold, just less cranking when she's hot.

 

[ToddJK]

On regular diesel right now and it does it. I would figure if it was bad fuel it would have more issue when cold. I am having the opposite starts great when cold takes about 3 blips of the starter switch when warm.

When you get a chance, could you do a video on a cold start and then again when the motor is fully warmed up? I just want to see exactly how long it takes to start warm vs cold.