Fuel pressure issues and high rmp white smoke poping

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Freds99

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Oct 18, 2011
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Ive been tracking this problem for 3-4 days now. First thing I did was put a ofv out of a known running truck. Checked the fuel pressure 15psi at idle drops to 0 at idles and goes back and forth between 15-0 at idle and if you rev it no load it goes to 0. Put another ofv in it and same thing. Pinched return line goes up to 55psi rev it and it drops to 30 if you drive it and get it up in the rpms it drops to 0 and starts smoking and poping. Put another ofv in it same thing. Put 2 more lift pumps on it one off a known running engine same thing. Next one was new from orilies. Fuel pressure up down up down with all ofvs in it and all the lift pumps. I can not figure it out. I've stumped a diesel injection service that as been around for years in stlouis 30+ years and I called schied stumped them. Any one have any suggestions? Engine is a 12v out of a 94 160 pump. Also have pressure tested fuel system no leaks. And have set and rechecked timing set to 17.5*. Also have put another set of injectors in it too.
 
Have you dropped the tank? Sounds like a restriction on the intake to the lift pump.
 
Is there a screen on the fuel pickup in the tank? The dodge has one and it does get plugged. Also a screen on the fuel heater.
 
It has a beans sump in the bottom of the tank. This is in my excursion.
 
Freds99 said:
It has a beans sump in the bottom of the tank. This is in my excursion.
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Tank not properly vented developing a vacuum? Pull the fuel cap and see what happens? See if you can draw it out of a bucket or something.
 
Fuel heater deleted it is 3/8 push lock all the way to the front and then stepped up to 1/2 to the lift pump.
 
I gutted the fuel cap and you can blow through it. Also I've left it off and it don't make a difference.
 
I would say see if you can draw it out of the bucket. If it still does it, I would say only thing left injection pump.
 
Ill try that tomorrow. I was thinking about swapping some dvs out of another running pump I have. If not I'll put that pump on there. I'm just wondering what could be bad in a p7100 to cause fuel press to go up down up down up down 15-0 at idle
 
How many miles on the pump. Can you put a pusher pump on it and see if it does it again. A pusher pump between the tank and the lift pump.
 
I don't know the miles on it I was told around 180 was a Craigslist buy. I when the head was off it looked nice in the cyl so I'm thinking 180 sounds about rite. The over flow valve in the pump originally when I put it together has a cracked spring? Is there any way low fuel pressure in a p pump for a long time could do internal damage that would make fuel pressure swing?
 
I would think low fuel pressure might have some affect on that. The pump is lubed by oil. But the barrels and plungers might have some wear on them. I would swap it and see what happens. Try the lift pump idea i had.
 
well im still having some fuel pressure problems but ive gotten it to quit runing out of fuel. I put a fass ddrp on it that was on a 24v that was "sent" back to fass to up the pressure when the guy p pumped his truck. Im just now sure how they uped the pressure? there isnt a bypass in that pump is there? its one of the older squared red pump head one. Now with the fass I had a bosch ofv that I streched the spring and it sits at 35 with the key on. as soon as i start the truck it drops to 25 then driving normal I see 10-15 I can suck it down to almost 0 if I lay into it. The pump has 131 dvs, stock injectors, and a 0 plate slid almost all the way forward I moded the afc ( replaced the cupped washer with flat washer) and set the star wheel to just touch the end of the housing at 35psi the truck barely smokes at all its not just dumping fuel the fass pump should me able to keep up? Im lost and after 2.5 weeks of working on it im about to the point of burning it to the ground or taking the engine out and puting a VE pumped engine in it.:bang
 
running low press can damage the barrels and plungers i would take it off and have it checked on a benchstand
 
had kinda same problem with mine .. found out it was the factory pick up tube sucking closed some .. not sure where your pull fuel from or at the bottom of you sump.. just an idea ..
 
Ya I'm sucking fuel from the bottom of the tank 3/8 Ez couple hose to the fass then 3/8 to the injection pump.
 
ok tomorrow is the day. Im going to pull the ip and put a good pump that I know works cause I drove the truck befor I took it apart.

cause with the key on fass running If i pinch off the return it will go to 40psi. as soon as i stary the truck it goes to 25psi with the return pinched if I touch the throttle it will go to 15psi there is something internally F`d in the pump.
 
Do you by chance have the DDRP serial # because those pumps are rated for stock 24 valves?
 
I thought it was a ddrp but it is a stand alone hpfp no model number on he tag but the serial is 00936.
 
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