Low fuel pressure, poor performance

dgr

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Truck has what I consider less than stellar performance. It smokes the freeway at night pulling a mild grade. It will smoke a lot accelerating in first gear, especially if I have had it idling for 10 minutes. It does burn oil. Say a quart in 500 miles. The exhaust does smell oily.

Just checked my fuel pressure at the schrader valve. It is running about 2.5 to 3.5 PSI. I don't have bubbles when it is idling but I do get them when I throttle up and let off the throttle.

It has a new air filter. Does the same with the air filter housing removed. It has a new fuel filter. Timing on the fuel pump was retarded. I advanced it and when I checked it with my Ferret, it was at 10.9 degrees. This did improve performance.

Truck starts immediately. One time, during a warm start, it stumbled and took maybe 5 seconds of cranking to get it started. That was after a couple hours of sitting. It has never repeated that.

Truck idles smooth as can be. On my actron timing light, it is a steady 660 RPM. Cracking any injection line will drop it to 640 or 650 RPMs.

When accelerating, it feels like a gasser running on 7 cylinders. There's a little bit of that vibration feeling you get when a gasser is missing. Maybe I am imagining that.

I changed the injectors out with some rebuilt Uhaul injectors. There was definitely a very wet injector with the old ones, they had gray paint so I expect it was time to change them at 140k miles. All return lines and caps were replaced. Olive for the return line was replaced. Exhaust quit having that burn your eyes with raw diesel going on after the injectors were changed.

Compression was taken cold. All cylinders were at 440 to 455 except one was at 475.

It seems to me like there is an excessive amount of oil in the intake. I will likely change the CDR since it appears to be original.

To recap:
Newly installed rebuilt injectors. New return line kit. New air and fuel filter. Lift pump pressure seems low to me. Burns oil. Smokes grey/white on acceleration. Compression is good.

I do have a Uhaul rebuilt IP sitting on the shelf.

My thoughts were to replace the IP prior to seeing what the fuel pressure was. Now I'm wondering if the fuel pressure is giving me grief and if I should replace the lift pump? Or screw it. Start at the grill and work my way back to the tail pipe replacing everything on the way.
 

icanfixall

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My feeling are the injection pump ia just as bad as the original injecters you replaced are. So change out the injection pump. Time the engine to 9.5 or 10.00 and test it. Sounds like you have a solid engine but a poor pump problem. The fuel pressure is fine but... ^ or 7 lbs would sure be nicer to have. What might be going on is the injection pump is starving for fuel at higher rpm useage.
 

dgr

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Thank you. Just got the pump off. It has a Standadyne Remanufactured Tag riveted on there. Does that tell me anything about the pump? It also looks like it was leaking out of the advance piston. We'll see tomorrow what a new (to me) pump does for it.
 

riotwarrior

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Are you able to say...run the gauge out on the hood of truck...TAPED down so you can test at WOT while running down the road? You may find the fuel pressure inadequate for load.

I agree with Gary, IP is likely suspect, though IP and lift could be a combination culprit...the lift pump is the simple one to test at WOT and under load as I mentioned...thus easily confirmed or eliminated from the situation.

Al
 

FordGuy100

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Yup, I would think under load your fuel pressure is dropping off by a good amount. I thought stock lift pumps put out like 6-7psi?
 

dgr

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Giggity.
Got the IP and lift pump changed out. It is a different truck now. Black smoke on demand. I will drive it for a few days to make sure the lines are bled then time it.

Question? How are you supposed to get the ip out? There isn't really enough room between the pump mount and the air inlet to ease it back. Plus the rear lines hit the firewall. What is the tube on my lift pump to filter line? It has one wire that I swear goes into the valve cover gasket.

Anyone with a c6, you can do it without disconnecting the kick down at the transmission but I wouldn't recommend it

I had to really bear down on the lift pump inlet to get it to stop dripping. I expect that is going to cause some grief later.
 

icanfixall

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To remove the injection pump its easiest to remove the feed line from the filter. After all the three bolts are out and the three nuts are removed just move it towards the air horn. Once its cleared the housing turn it towards the passenger side fender. then lift it up out between the left stud and the top stud on the gear cover. Its got plenty of room for that. Install it the same way in reverse. I leave all the hard lines on the pump and just slide it up and out. Even with my turbo its able to speak out.
 

Kevin 007

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I always disconnect the lines, just be sure to mark or make a diagram on which line goes where and in what order they came off, then install em in reverse order.
 

dgr

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Thank you.

I got it in and out but it was a bear. I think fighting with the down shift lever wasn't helping anything and there were a couple of lines that ran into the air horn sooner than I was hoping.
I would rather do the IP again than scrape the lift pump gasket after who knows how many miles and no sealer to make it release easily.
 

riotwarrior

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I would rather do the IP again than scrape the lift pump gasket after who knows how many miles and no sealer to make it release easily.

I assure you if you used elephant snot on the lift pump and a year or ten later decide to um...remove the lift pump...it's NOT GOING scrape off any easier than what you had to deal with on this run....*****!!!! ELEPHANT SNOT gooooooood!
 

dgr

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Napa had no aviation gasket cement on the shelf. I am very anti-silicone so grabbed some hylomar. I've used it for years and like how it is kind of brittle when scraping it off.

I kind of buried this question. What is the tube on my lift pump to filter line? It has one wire that I swear goes into the valve cover gasket. The metal line from my lift pump to the filter head has a larger diameter tube around it that is closed on both ends. It is about 4 inches long and has what appears to be an electrical wire coming out of it. It appears that wire runs into the valve cover gasket. Anyone know what this is?
 

dgr

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I did not know I had one of those. Of course, until I was laying under there for an hour today scraping that damnable gasket, I didn't know I had a block heater but noticed the three prong plug up under the bumper. Does the fuel heater really do much? With the amount of fuel that is passing through there and most of it getting returned to the tank anyway, is it really doing anything?
 

opusd2

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The fuel line heater does help, if it is in decent shape. I've already had to pull one apart to verify the thermal limiter's operation, but they do make a difference. Different designs have better or worse performance though.

To crudely verify if it even heats up, you can run a hot lead to the connector on the wire running off the heater and cup your hand around the thicker diameter tubing.
 
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