LP Glow Plug Priming Mod Questions concerning starting

[orrum]

OK here goes. I installed a OPS bypass mod on my 6.2 last week and while into it I also put a LP momentary priming switch in the cab. Originally I was going to use the waiting to start glow plug LP priming mod but changed my mind due to the ability to use the momentary button switch to bleed my filter change. I now think this was a fortunate accidentally GREAT decision! My truck starts very easily, like I mean it hardly goes whump and she is up and running and right off idles smoothly once I kick the hi idle in by tapping the accelerator. I wanted the priming button for my later conversion to a wvo blend, its harder to start. I now have been using my primer button b4 starting by mashing it while the glow plug waiting to start is lit up and I can tell that the engine does not start as easy and now smokes on starting so today I started it with no LP priming button usage and she fired right up with no smoke like b4 I started using the button, even after sitting all nite. Now today I installed my Glowshift fuel pressure gauge and was really pleased with the info it provides. I used a needle valve snubber to be able to fine tune the snubbing effect so that my electric sensor would not crap out like everyone reports and also to get nice slow steady movement of the needle during pressure changes up and down and to also not have the needle jumping and vibrating which makes the reading of your pressure so difficult. Immediately I noticed that while the truck was shut off the gauge held a steady pressure, it was at 6 lbs at a idle and when shut down it climbed up to about 10, u know how the LP runs for a few seconds after u shut the truck off, this increases the pressure. I took about a hour to put all the tools and other stuff up from my installing the gauge etc. When I went back to start the truck and test drive it the gauge was still showing about 10 lbs of pressure. I just checked it again after it has been sitting several hours since my test drive and its still holding pressure. I played with it by using the primer button with the truck shut off and the LP would pump it on up towards 15 lbs and I got concerned and stopped without seeing how high it would go. This is with who knows how many miles on the filter. I just got the truck and have not changed the fuel filter yet. I know this is a long post but hang in there plz. So here is my guess, observation, concerns and maybe advice. I think my hard rough starts were due to using the primer button and having too much fuel pressure at ignition, I also think the pressure caused the smoke. Now that I have a fuel pressure gauge I can check pressure prior to cranking the starter and find a good starting pressure in lbs. I suspect whatever the pressure is tomorrow morning will be the desired pressure since it starts so good that way. Then if it sits long enough to leak the pressure down I can just pump it up to that pressure to start. I will report on this as I experiment. Now my concern for everyone that has done the waiting to start glow glug mod is this.... are u pumping up too much pressure by running the LP the entire glow plug cycle???? Remember I was pushing my primer button the same amount of time as the glow plugs were on. My question is this..... what damage or issues can u cause by having too much fuel pressure and smoke at startup??? Seems like I read somewhere that a DB2 cant handle too much pressure, can someone fill me in on this plz???? I imagine too much pressure means peeing out the injector or too much fuel out the injector which would wash down the cylinder walls. My thought is if u do the waiting to start glow plug LP priming mod u really do need a fuel pressure gauge to track all this. Personnaly I am a newbie to diesels but I have come to the conclusion that LP fuel pressure to the IP is super critical and most 6.2 and 6.5s dont have a gauge and dont have a clue what the consequences are of not having a fuel pressure gauge. Please dont kill me folks I am just trying to help. Thanks for reading this and giving me your thoughts and observations on this. Oh and by the way cold hard facts are really appreciated! Thanks again.

 

[ak diesel driver]

IIRC db2s like about 8-9 psi and too much pressure might be affecting the advance

 

[orrum]

AK do u think I am onto something cause I sure am glad I have a manual priming momentary button and not a glow plug mod for my LP. My old girl does a nice job and I dont want to confuse or damsge her!

 

[NVW]

Don't worry about peeing out the injectors with LP pressure. The injectors open at about 2000 psi depending on setup.

 

[orrum]

ok thats good 2 know. Got any idea where the smoke comes from. I always hear on here that smoke means too much fuel and the fuel isnt being burned completely.

 

[buddy]

LP pressure will not affect fuel out of the injectors, they are isolated within the IP and the injector does not pop until 2000psi. They do have a relationship though, with the timing on the mechanical IP. Timing advance is controlled by internal transfer pump pressure and housing pressure. Transfer pump pressure increases with RPMs from about 30 to 120psi. It is possible if your LP is going to 15+ psi that the IP housing pressure to transfer pump pressure ratio is causing less advance.

It could be coincidence, repeat the results to gain confidence in the data consistency. You can try unplugging the cold advance solenoid and see what affect that has as well.
Do you hit the pedal at all when starting?

 

[orrum]

Gmornin Buddy! Thanks for looking at this. I tap the pedal after it starts to make the fast idle thing lock in. It smooths right out as soon as u hit the fast idle. Should I tap the pedal before starting to make the fast idle work before starting?

 

[orrum]

Hey Buddy this is off topic but now that I have my gauge installed I want to do my oil change and fuel filter change. I am going to put the oversize oil filter on thats in your writeup and I have the Wix number. What wix number should I get for the square fuel filter and could u tell me how to change it plz? I have looked but cannot find info on the square filter, only the more modern 6.5 filter change. I have read that the square one messes up and leaks easy so I want to do this right. Also could u draw a picture of the fuel flow because once I get used to the new filter and the pressures it gives me and all I want to put a BIG 6 micron water separater filter and mount in before the factory filter and I dont know which fuel line to cut to extend over to the fender well. Its very hard for me to get back there and see what goes where. After I did the muffler and snorkle removal mod like yours I now have a good spot to mount a bracket over there. How close above the exhaust manifold can I put the mount and filter? I am wanting to use the exhaust to slightly warm the wvo blend, what I am after here is to avoid possible gelling in winter by heating the filter plus get a little thinner fuel. I know this is a lot of questions but I am making progress on this project so far with no catastrophys due to all yalls help here at The Truck Stop. Thanks again. I will report on pressures and starting behavior.

 

[Acesneights1]

The pedal tap is because the plunger for the throttle isn't strong enough to push the rack by itself. They all do that. Both mine do.

 

[orrum]

Here is a update. 24 hrs after turning the truck off the pressure had leaked down to 4 lbs. I turned the ignition on and when the glow lite went out I cranked it and she fired right up no problem. Later in the day I got in and the pressure was at 5lbs when I turned the ignition on so I tried tapping the pedal b4 cranking to set the hi idle and it stumbled and turned over several times and then started. Later I went out and the pressure was @ 5 lbs so I hit the primer button for a couple of seconds, not nearly as long as the glow cycle and it went up to 12 lbs before I could let go so I then cranked it and hard start with rough idle and smoke. It cleared up in a little and smoothed out. I realize these trucks are all individuals but I think too much fuel pressure at startup makes for a hard smoking start. I will continue to play with it. I need to let it go several days without starting and check out what happens. It usually takes several cranks and maybe a second attempt @ start if it sits for 4-5 days. The primer button will probably be a good thing then but only a couple seconds and the LP will get u 6 lbs. U gotta stop b4 it gets to 6 lbs since the needle valve snubber causes the needle to go up slow. U can always hit the button for another second.

 

[buddy]

I have not ever dealt with the box fuel filters. Aces might know some about them though, what best to use and how the fuel flows.

The poor start after setting kind of points to having another issue, which might contribute to the smoke and problems after priming. Sounds like possible glow plug or injector issues, or IP not quite working right, but good enough. Or maybe priming will help. Having a functional OPS alone typically helps, just because then you actually have pressure in the line when you shut down and it goes for a couple seconds more. If the OPS wasnt working and the IP would be sucking a vacuum while running and left with less fuel readily available on startup.

 

[orrum]

Update truck has not been started since Saturday and fuel pressure still holding at almost 5 lbs. I guess thats good? Gotta mow yard 2moro so gonna fire it up and move it outa the way. Usually harder to start and smokes at first when it sits for 4-5 days. Gonna use the LP primer button to pump it up to 8 lbs and see how it starts.