Suction Side Air Leaks

[MrMarty51]

I thought I had a video of the clear return hose but it didnt work out.
At about 1600 RPMs there is an occasional stutter.
At about 1900-2000 RPMs there is near a constant flow of air into the clear return hose and engine runs like crap.
I went through and installed hose clamps on every connector and tightened them all down real good, didnt change a thing. Lifted the box and tightened everything over the fuel tank. Installed clamps on the fittings under there too.
The fuel sending unit and pipe are new from Leroy Diesel.
New AirDog lift pump system.
My son was watching the clear return hose and I was under the truck holding, shoving, moving and wiggling the suction side O-Ring fitting that plugs onto the lift pump. Didnt seem to make a difference.
Filters are tight and the water drain cock on the water separator filter is tight.
I just dont know what else to look for.
Anyone have any ideas where to look next ? ? ? ?
Oh yes, fuel tank is 100% full and all tests are with the fuel cap loose.

 

[MrMarty51]

That last picture is of the pressure regulator return to tank hose and fitting.

 

[ak diesel driver]

Get some clear tubing and work your way back to the tank. At every joint add clear tubing if there's still air keep working back to the tank..

 

[MrMarty51]

Get some clear tubing and work your way back to the tank. At every joint add clear tubing if there's still air keep working back to the tank..

Good plan.
Be next week now. Tomorrow and Sunday is reserved for the Triumph.
If that motorcicle is removed from the garage I could be doing this work inside.

 

[MrMarty51]

 

[MrMarty51]

The Els that makes a sort of a box figure was so I didnt have to make a large loop with the hose.

 

[Twisted Steel Performance]

That just gives more places for air intrusion...

 

[MrMarty51]

That just gives more places for air intrusion...

Might be a good plan to start at the tank fuel supply pipe and replace the entire conglomeration with just one hose then see what happens.

 

[jrsavoie]

Might be a good plan to start at the tank fuel supply pipe and replace the entire conglomeration with just one hose then see what happens.

Is there any area you can isolate and put air pressure to?

I've added ball valves and pressure gauges to things and then pumped them up.

How much pressure can the fuel system stand between the tank and the IP?

I think I might be suspect of your IP or FFM. Possibly fuel pressure gauge sending units.

 

[MrMarty51]

Is there any area you can isolate and put air pressure to?

I've added ball valves and pressure gauges to things and then pumped them up.

How much pressure can the fuel system stand between the tank and the IP?

I think I might be suspect of your IP or FFM. Possibly fuel pressure gauge sending units.

Everything from the AirDog forward is under pressure, more pressure than the suction of the IP so the inlet side of the IP should be under greater pressure than what suction can provide at about 8 to 10 pounds so if there was a leak to the inlet side it should show up as a pressure leak at the FFM or the IP.
I will however pressurize the tank and see if I can detect a leak.
I do have a air pressure regulator and I’ll adjust it to a couple of pounds then apply pressure to the fuel tank. Even if it takes a couple hours for the leak to appear.

 

[Will L.]

Gm says 2nd place for clear hose is between ffm & ip. If you get air after ip but none before- ip is the problem.

Ive said before if I could I would use clear 100% of the way tank to ip & back IF the clear tube could withstand the pressure and rubbing and was rated as fuel hose like the stuff from fuel-line.com (not rated for the rubbing is the only downfall)

 

[Big T]

Circled in red should be your incoming fuel line to the lift pump. The o-ring here was always damaged with advanced age. The other fitting is your return line. I replaced both with AC Delco, which will cost you $200+, but you could just try new o-rings which you can get at Napa for < $10.

The rest of this run is at your lift pump.

If you were Will L go large with the clear line. His other suggestion going clear from FFM to IP is good stuff.


BTW what is that 3rd line at the top for?

 

[MrMarty51]

Gm says 2nd place for clear hose is between ffm & ip. If you get air after ip but none before- ip is the problem.

Ive said before if I could I would use clear 100% of the way tank to ip & back IF the clear tube could withstand the pressure and rubbing and was rated as fuel hose like the stuff from fuel-line.com (not rated for the rubbing is the only downfall)

Guess thats the next step.
Set the air pressure regulator at ten PSI and no leaks nor seeps anyplace after about a half an hour of constant pressure.
And fuel tank is full enough that the pressure was pushing fuel out past the rags on the filler neck.
Box is lifted enough to reach on to the top of the fuel tank at the sending unit and all was dry in that area.
On wards to the clear hose between the FFM and the IP.

 

[MrMarty51]

Thank You @Will L.
Clear hose between the FFM and the injection pump and there was no air bubbles that passed through that hose.
The 1/4” return hose passed plenty of bubbles with the RPMs running up to the 2500 RPM range.
What say is the preferred pump.
QST has brand new units in stock. Would one of those pumps be problematic because of the extended shelf life ? They are near $2700.00
They also have remanned pumps from Flight Systems for a lot less. $850.00.
I would go for the new unit if it is thought that they would be trustworthy.

 

[Will L.]

No aeration before ip hut has it afterwards means it is the ip. If this is an old ip, you can try snugging up the screws you can get to & cross your fingers.
Most likely it’s the pump entering its death bed.

 

[MrMarty51]

No aeration before ip hut has it afterwards means it is the ip. If this is an old ip, you can try snugging up the screws you can get to & cross your fingers.
Most likely it’s the pump entering its death bed.

Dang. It was a reman from unknown regions.
The old pump was running good, just throw that advance code every once inna while.
Guess this will be a buy once cry once again moment and go for that new unit from QuadStar tuning.
The description tells that they are dismantled, new seals and gaskets, tested on the stand for functionality.
Damn, credit card just keeps getting thicker.

 

[Will L.]

imo talk to a few folks more knowledgeable about the ds4 before making the jump.
@Rockabillyrat and John @ Quadstar come to mind. I learned enough to be dangerous with the ds4 & where most of my time with them was at, down time of the truck was way more expensive than cost of an ip & labor. So we swapped them out without a doubt. Usually I would physically swap and another guy who loved computers, tuning, and other magical pixie dust reset it up for timing and such.
But modern prices - I would hesitate before buying.

 

[MrMarty51]

imo talk to a few folks more knowledgeable about the ds4 before making the jump.
@Rockabillyrat and John @ Quadstar come to mind. I learned enough to be dangerous with the ds4 & where most of my time with them was at, down time of the truck was way more expensive than cost of an ip & labor. So we swapped them out without a doubt. Usually I would physically swap and another guy who loved computers, tuning, and other magical pixie dust reset it up for timing and such.
But modern prices - I would hesitate before buying.

Only other choice would be the DB-2 pump for about $1750.00 for new and i think the reman was $725.00 or some such.
That would require a transmission controller and I think those are not an easy thing to program.
I would love to do the mechanical pump.
I imagine that QST also programs the PT control module to accept that pump.

 

[Will L.]

It’s hard for me to not promote the db2 every time I can. But already having the tooling, scanner, know-how etc means 90% of your pain is done.

My friend Charles says: The enemy of good is better. If I had listened to that advice years ago my hummer would have been on the road long ago.

 

[MrMarty51]

I sent an email to QST about if there is any warrantee on those new DS4 pumps and waiting for a reply.
See how that goes before I make the decision over the new or the Flight Systems remanned pump.
The price of the reman units makes it mighty tempting to go that route, but then, if the reman units does the same as this reman unit and I have to wait for a replacement then there would be no time left to make it to Ohio and to the function over there that I would like to attend, and, My brothers childhood friend has to be back to his home by the 29th of June to pick up his daughter at the Billings air terminal.