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2500ctd

Hard starting/Fuel drainback

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OK I posted this on CF. Thanks Mike for the tip on the Overflow valve. I just finished reading your testing on it and then rechecked to see you mention that lol.

Quote is what I posted over there:

I just got my truck going again after fixing the 1/4 tank issues. I used a DSV on my intank module. Now it doesnt start unless I bump the key to run the LP for 25 secs. The fp builds up and then it fires right up. Same thing when hot. If it sits its crank and crank. restart it quickly like in a drive through, fires right up. My lp did start to die on me so I swapped that as well. I fixed some fuel leaks I had at the lp connections. Wonder if I should reinstall those leaks? Posted Image

Wiped all the fuel fittings I can see, except the return from the back of the head, and nothing seems to weep any fuel. FP stay high for a couple minutes aftershut down as well. No drips on the ground either.

So any tricks on finding fuel drain back issues? I am dreading its in the tank. No fun pulling a tank on a QCSB. really thinking of pulling the bed next time. Posted Image

Truck starts and runs rough for a few seconds then clears up. Well has a small rolling idle, but that came with my bigger injectors. I am going to loop some clear hose between the filter and VP and see if air is in the line. Just because I have FP doesnt mean there cant be air in the lines.

Any tricks/tips pitfalls for the fuel drain back issues? Posted Image

I did some testing according to the bluechip diesel VP44 diag page and came up with it being a fuel delivery problem. Like I said I only installed a DSV replaced the supply line to the filter, cleaned the prefilter and replaced the walbro with another one, and redid the regulator. The fuel lines used to weep fuel and would drip ocasionally. It no longer leaks but now the hard starting. Used to fire up right away. Not sure if its in the tank, or the new line or? I havent tested the overflow valve as I dont think that would cause this. Or would it?

PICs and narration:

3/8 clear tubing between the filter housing and the vp Long enough to loop up under the wiper.

Posted Image

Posted Image

This is the truck idling. Air is somewhere getting in the system.http://s12.photobucket.com/albums/a207/CrazyMoparGirl/Mobile%20Uploads/?action=view&current=0718111045.mp4

A quick run. Got on it and the air gets worse. How with an electric pump?

Posted Image

After shutdown, the fuel draining back to the tank I hope. Nothing on the ground so its gotta back to the tank. The bubbles appear from the filter housing. Why I dont think the relief valve is stuck open.

Posted Image

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No doubt about air in that line. You have a leak on the suction side of your lift pump. It might be enough that it would be wet from fuel weep while sitting at rest - hard start is probably from that feed line being empty. Be happy that you only have a hard start and not a no-start, the 12v pump doesn't self prime!

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I will get better pics.IIRC, the pics are showing how I have the line inbetween the stock filter housing and the VP. The rest are cell phone vids. Had to lift on the run as I came around a corner and a cop was coming the other way. first time I ever seen one there. He did look at me funny with the hose up under the wiper. LOLHow do you go about looking for a suction side leak? I did check and saw no fuel after it was sitting for a bit. I am going to run a external line to the pump to bypass the tank pickup. Hope it isnt in the tank itself. Only half tank so it could be the connection near the top.

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No doubt about air in that line. You have a leak on the suction side of your lift pump. It might be enough that it would be wet from fuel weep while sitting at rest - hard start is probably from that feed line being empty. Be happy that you only have a hard start and not a no-start, the 12v pump doesn't self prime!

Just thinking out loud here, but have you tried connecting the clear line between filter cannister and pump? If so, what did you find? Is there still a sign of air bubbles? You can for sure eliminate the possibility of it being the drain valve with this approach. I have a similar problem with the valve dripping on occasion. It would be interesting to see what the result would be. You might want to shorten up on the hose, due to the uncertainty of the NPSH(net positive suction head) of the pump.

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Ok more troubleshooting. I filled a 5 gal bucket and ran another clear hose from the pump suction to the pump. Clear solid fuel going into the pump and a minute so of running the line bnetween the filter and vp was clear of air as well. That narrows it down to before the pump. Hooked the clear line from the DS to the pump and all kinds or air. One more thing I can try is to rehook up the old DSII. I didnt do that as I got irritated with the possibility of having to drop the tank again. If the old draw straw is air free.....:mad: If so how to find where the actual leak is? Thinking I might just get a jeep liberty canister and call it good. Are those 3/8's pickup?

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That narrows it down to before the pump.

being an air leak as opposed to a fuel leak already had it narrowed down to pre-pump before you did any other testing. pressureize the tank like Mike said, or just spend $100 and replace the fuel lines from the tank to the pump. When mine went the rust was near the bend at the floor/firewall area but it really could be anywhere. If the fuel lines are rusted through it would probably be a good time to replace your hard brake lines as a preventative measure. My front crossover hard line, fuel supply hard line, and the original remaining piece of front-to-back hard line all failed within a year of each other. The only original steel plumbing on my '97 are the hard lines on the rear axle...

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being an air leak as opposed to a fuel leak already had it narrowed down to pre-pump before you did any other testing. pressureize the tank like Mike said, or just spend $100 and replace the fuel lines from the tank to the pump. When mine went the rust was near the bend at the floor/firewall area but it really could be anywhere. If the fuel lines are rusted through it would probably be a good time to replace your hard brake lines as a preventative measure. My front crossover hard line, fuel supply hard line, and the original remaining piece of front-to-back hard line all failed within a year of each other. The only original steel plumbing on my '97 are the hard lines on the rear axle...

what did you use to replace the hard lines with? i notice rust on my break lines neear the fuel tank when i installed myAD>

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diesel-rated rubber line all the way from the tank to the pump and from the return to the tank. I had a couple feet left over from 15' purchase on my extended cab long bed 12v. I won't say what I think the line sizes are because I didn't post it where I thought I did. the google knows, and I think it's Geno's that even sells the set of lines, among a few other places. The correct fuel line is pretty expensive. If you're not spending $5-8+/ft, you're getting cheap gasoline rated stuff, you want fuel and oil stuff so it lasts the life of the truck without breaking down.

protip: way easier than dropping a then-full tank:

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i meant the brake lines. replaced all but the fuel return line weh i installed the AD. did not mean to hijack the thread.

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being an air leak as opposed to a fuel leak already had it narrowed down to pre-pump before you did any other testing. pressureize the tank like Mike said, or just spend $100 and replace the fuel lines from the tank to the pump. When mine went the rust was near the bend at the floor/firewall area but it really could be anywhere. If the fuel lines are rusted through it would probably be a good time to replace your hard brake lines as a preventative measure. My front crossover hard line, fuel supply hard line, and the original remaining piece of front-to-back hard line all failed within a year of each other. The only original steel plumbing on my '97 are the hard lines on the rear axle...

:lol: Yea I guess it did. I put all new lines in already. Biggest thing I did was a DS5. Last thing was swapping back to the old DS. That works fine just back to watching the 1/4 tank thing again. Gotta get my other truck back on the road before I tear into this one again. For a week I had both trucks down and the motorcycle in the shop. Not a fun week. LOL Now just one truck down. :stuned:

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