I've been loosing prime lately.

 

* Park nose downhill, starts fine - uphill, hard to start

* Pressurized the return lines from tank filler neck, no fuel leaks visible (did hear a hiss from the top of fuel module - guessing take vent)

* Checked all inbound and return connections, everything is dry (replaced sealing rings/grommets for banjo fitting in back of head and tee 10 months ago)

* Oil level is fine

 

So at this point I feel like all external fuel lines/connections are sound.

 

I drive like an old man most of the time.

However the other night, I turned the quad up a little and got on it for a few seconds. 

The next couple of days I notice the hard start issue.

 

Questions:

 

* Would getting on the throttle blow out a crossover tube or injector O-ring?

* Can you have a faulty O-ring and not get fuel mixing with motor oil?

 

The cross over tube o rings wont mix the oil and fuel. The injector o rings will. My last hard start issues were the cross over tube o rings.

Any way to test the cross over tube O-rings, short of pulling the tubes?

 

I dont know any way to test them. They are fairly easy to change though and cheap to buy. 

Thanks dripley.

I'm also curious if "spirited" driving increases pressure on these and can cause failure?

That on its own I would not think so.  I get a bit spirited myself at times. Mine had a lot miles on them when they failed, 100k+ maybe. Any idea how old yours are?

Edited October 5, 20195 yr by dripley

I've got maybe 20k on mine. 

Replaced the CT O-rings at the same time I dropped in DAP 100hp injectors.

 

 

Thats pretty young to be worn out. Unless you might of damged one or when you installed them. I did see some damage to mine when mine was hard starting. And I had pulled those tubes a couple times without replaceing the o rings.

 

Weak batteries or starter can mimick the issue but the nose up and down thing points to the fuel system. 

Injector o-rings will mix fuel with oil. Now crossover tube o-rings will leak fuel out on the manifold.

2 hours ago, Mopar1973Man said:

Injector o-rings will mix fuel with oil. Now crossover tube o-rings will leak fuel out on the manifold.

When mine was doing it I saw no fuel on the manifold. But you would think it would be there. Small enough leak not see the fuel maybe but let air in is possible but I was surprised with how shitty mine got there for a while that I did not see fuel on the manifold.

DAP sells the cross over o-rings. Typically supply new crossover o-rings with injectors.

Should be able them at a diesel shop nearby if you have one. Might be worth a try after all else you have done.

 

I still believe its in the fuel system some where.

Edited October 6, 20195 yr by dripley

Thanks for the help/suggestions guys!

 

Close friend manages the local diesel turbo/injection shop and I'm sure he'll have what I need.

Going to drop off my injectors to have them pop tested and evened out.

Might as well since I'll have things apart.

 

 

On 10/4/2019 at 1:22 PM, Octafish said:

I've been loosing prime lately.

 

* Park nose downhill, starts fine - uphill, hard to start

* Pressurized the return lines from tank filler neck, no fuel leaks visible (did hear a hiss from the top of fuel module - guessing take vent)

* Checked all inbound and return connections, everything is dry (replaced sealing rings/grommets for banjo fitting in back of head and tee 10 months ago)

* Oil level is fine

 

So at this point I feel like all external fuel lines/connections are sound.

 

I drive like an old man most of the time.

However the other night, I turned the quad up a little and got on it for a few seconds. 

The next couple of days I notice the hard start issue.

 

Questions:

 

* Would getting on the throttle blow out a crossover tube or injector O-ring?

* Can you have a faulty O-ring and not get fuel mixing with motor oil?

 

 

Most likely blew out the front seal on the vp-44. That's exactly what happened to me. I went to pass someone and went from 1,250rpm to 3,300rpm's and that was enough to do it. Avoided the accident though! Anyways the front seal took a crap. It took 4 months before the oil level started to rise in the engine. I went through the exact same testing and found that plugging the truck in nose up it fired up just fine because the heat was on the block on the front seal. Nose down the tank is higher then the vp, and thus there was no air gap for it to go into.

If it matters my pump was painted black and there was speculation that the dodge dealership that installed it installed a Chezch rebuild that was probably never build right.

4 minutes ago, pepsi71ocean said:

 

Most likely blew out the front seal on the vp-44. That's exactly what happened to me. I went to pass someone and went from 1,250rpm to 3,300rpm's and that was enough to do it. Avoided the accident though! Anyways the front seal took a crap. It took 4 months before the oil level started to rise in the engine. I went through the exact same testing and found that plugging the truck in nose up it fired up just fine because the heat was on the block on the front seal. Nose down the tank is higher then the vp, and thus there was no air gap for it to go into.

If it matters my pump was painted black and there was speculation that the dodge dealership that installed it installed a Chezch rebuild that was probably never build right.

So it started fine nose up or down?? Just a bit confused as to how you wrote that.

3 hours ago, pepsi71ocean said:

 

Most likely blew out the front seal on the vp-44. That's exactly what happened to me. I went to pass someone and went from 1,250rpm to 3,300rpm's and that was enough to do it. Avoided the accident though! Anyways the front seal took a crap. It took 4 months before the oil level started to rise in the engine. I went through the exact same testing and found that plugging the truck in nose up it fired up just fine because the heat was on the block on the front seal. Nose down the tank is higher then the vp, and thus there was no air gap for it to go into.

If it matters my pump was painted black and there was speculation that the dodge dealership that installed it installed a Chezch rebuild that was probably never build right.

You know, I wondered about something failing in the pump causing it to loose prime.

 

I just checked the cross over tube O-rings and feel like they are fine.

So the pump seal could be suspect.

 

Definitely not something i have experienced nor would have thought of.

On 10/6/2019 at 6:41 PM, dripley said:

So it started fine nose up or down?? Just a bit confused as to how you wrote that.

 

It would start up fine nose up only when i left the block heater plugged in. if I didn't' plug it in, it would loose prime. Even thought it was going on May, I had to leave it plugged in.

 

It took maybe 2,000 miles of driving to determine what the problem was the last 1,000 miles required oil changes every 500 miles or so. I was gaining about 1'' in crank case.

 

A good way to test is to use a paper towel and see if you can see a highlighter green hailo around the oil on the dipstick. you check it like you would your engine oil, just wipe it onto the  paperwork and see after a few mins the diesel separates from the oil.

 

Bear in mind, that it took another 40,000 miles of oil changes for the diesel to finally stop showing up in my oil changes, because it was scrubbing all of my bearings clean inside the motor.

Fuel Injection shop says my injectors are very worn.

They pop under 230 bar, terrible spray patterns.

 

Also remarked how flat the O-rings were.

There was no resistance when I pulled them out.

 

These are the DAP 100hp VCO aftermarkets.

Have less than 20k on them.

I'm shocked they wore out that quickly.

 

All that said, can worn injectors and O-rings cause loosing prime?

18 hours ago, Octafish said:

Fuel Injection shop says my injectors are very worn.

They pop under 230 bar, terrible spray patterns.

 

Also remarked how flat the O-rings were.

There was no resistance when I pulled them out.

 

These are the DAP 100hp VCO aftermarkets.

Have less than 20k on them.

I'm shocked they wore out that quickly.

 

All that said, can worn injectors and O-rings cause loosing prime?

 

230 sounds really low, more likely 280. Either way they should be re-popped. Mine were around 280 when I pulled them around 33,000 miles.

 

Have them popped to 310-315 bar. I tell people that popping injectors is a normal ware item. Personally I popped mine to 325, and haven't had any issues per say. Now understand that when you get injectors set, they usually drop 10bar quickly, and that is considered normal. But with a truck without a tuner, you need to run lower pop, which is why allot of injectors are set to 300. I went higher knowing that after 45,000 miles i should see 290bar by then.

It could cause a hard start, but then it would do it all of the time.  

Kind of like myself the +75 HP DAP VCO (7 x 0.0085) injectors only made about 75k miles and were wore out and popping low. Typically what you'll see is the engine load drops seriously low at about 3% and the idle is excessive high like 850 to 900 RPM's that is pop pressure is TOO LOW. The ECM can't cut fuel morre, so the idle creeps up and the engine load is botttom out because it can't cut fuel. 

 

293 Bar (Bottom limit) <-> 300 to 305 bar (common for aftermarket) <-> 310 bar (stock pop) <-> Greater that 310 bar (MPG and longevity)

 

Like myself I'm popped at 320 bar on my 7 x 0.010 injectors. Touch 22 MPG once in awhile. I'm down to about 7% engine load at idle from the 13% I had originally when I installed so I'm about half life with these injectors. About the first 20k to 30k it stayed close to 11 to 13% but now starting to wear and lose its pop pressure at miles are racked up 1,000 miles per week.