98 GMC 6.5L TD hard start miss at idle and stumble but no stall - Diesel Place : Chevrolet and GMC Diesel Truck Forums
 
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Old 11-16-2015, 05:37 PM   #1 (permalink)
RagsNB
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98 GMC 6.5L TD hard start miss at idle and stumble but no stall

Hi all,
Been trouble shooting a hard to start missing stumbling truck. It feels like water in the fuel but there is not. Ran the usual fault checks thought it was lift pump as I replaced the tank a few weeks ago and thought maybe some crap got in pump after that and replaced it no change. Did the usual first thing replace the fuel filter....had a little wax like stuff at very bottom looked in bowl saw nothing but white base fuel was clear. Ran the fuel anti gel cleaner stuff in a fresh half tank still an issue. decided to pull the filter and replace it with another new one cause when I changed it it did not seat well so swaped it out for new one. Looked into bowl a little better this time and saw a strange white substance in bottom of bowl. I was hard to get out had to pry it up with srew driver it was like semi hard toffee. Check out the photo. It is 1/2 inch thick formed the shape of the bottom of the fuel bowl. was hard to pry out and came out like it was stuck taffy half hard toffee. Cant figure out photo insert.

Thoughts?
I replaced tank could it be a rust liner is on new tanks? Could it be sugar in tank? How do I clean tube from base of fuel bowl to T valve at front of engine to drain fuel. That tube is plugged as t valve wont drain anything and should pump fuel out when running. How do I post a photo?

Rags

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Old 11-16-2015, 06:09 PM   #2 (permalink)
RagsNB
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Ok figure out the photo upload here they are. strange stuff
Rags

Attached Images
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File Type: jpg Cambridge-20151116-01054.jpg (56.3 KB, 2 views)
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Old 11-16-2015, 06:31 PM   #3 (permalink)
HeavyChevy95
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Sounds like microorganisms and fungus growth, dead carcusses, and excessive amounts of umm by-products aka pooh..

Fuel treatments may kill or stop 'em, but does little to flush em away..


New Tank, new sender? If so, did you install a new Fuel Strainer (ACDelco TS 1012)?

Did you thoroughly flush the entire system when you replaced the fuel tank?
If not, possible you recontaminated the system ie quickly clogging the new incorrect gasoline sock.?.?

Ever run bio fuel or alternative fuels? If so, dont..

With engine running, there should be fuel pouring out of the WIF drain valve when opened. If not, typically indicates LP isnt working or is faulty..

Note your supposed to drain aprox a liter of fuel from the FFM every time you fill up, at least once a month. Thats how this system "strains" off free water that naturally collects in the tank.. This regular maint procedure isnt done on a regular basis if at all (not unless WIF lamp flashes ON) so its common to find a pile of crap in the bottom of the FFM housing.. If its been neglected for some time, the WIF drain port may be clogged full of it too..

Unrestricted return line is equally important..
A starving lift pump can quickly become damaged, even if its brand new.

Given how solidified that looks.. I would inspect the entire fuel supply ans return system for any more possible restrictions..

Good luck

Last edited by HeavyChevy95; 11-16-2015 at 06:33 PM.
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Old 11-16-2015, 06:45 PM   #4 (permalink)
RagsNB
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I replace lift pump today when I found that toffee crap. I ran bio fuel in it a year ago and had no problems and this all started after I put in new tank. I did not have the system flushed. Bio fuel sludge is more like thick fat or peanut butter this is like hard plastic that is plyable when warm. How would I clean that drain line nothing is coming out. I suspect its plugged as the toffee crap was filled up over inlet in bowl. Can I run a wire down the tube when engine warm? I will place a new strainer in it tomorrow. Sendor? you mean unit in tank....no. Just a fresh tank.

For me it does not look like micro or bugs its too plastic like almost like a polymer base plastic. Im expert so maybe wrong but when I worked in military and saw some old diesel tanks with huge microbs growing they were like sludge no hard plastic thats white.

As for the strain off some fuel I dont do it every month but normally ever season spring and fall and winter. I did it awhile ago and drained off fuel no water or crap just fine. Changed filter and next time I did it was this week and it did not work and then found that crap when I changed up the filter. The filter had about 10k on it max last time I used bio fuel was 2 years ago and drained the system and changed filters since then.

Rags

Last edited by RagsNB; 11-16-2015 at 06:55 PM.
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Old 11-16-2015, 07:40 PM   #5 (permalink)
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Looks like hard calcium deposit no idea how you would get that in your tank without someone putting calcium tabs in your tank though. also if you think someone is pouring sugar in your tank id get a diesel cap with a lock.
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Old 11-17-2015, 07:01 AM   #6 (permalink)
RagsNB
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Dead Diesel,
Not sure if its calcium as Id think calcium would be brittle crusty break apart this is like soft plastic or semi hard toffee. It has the colour of white silicon if i was asked to replicate it Id take toffee and lay it n the fuel bowl on a 90 degree day and it would melt into place and id coo it down to 60 degrees then peel it out semi hard. Any Bio fuel or sugar in the tank knowledge around here? I say sugar cause it is like toffee and almost white. it could be Bio fuel residue also as this truck ran bio fuel last year but gave me no problems for a year of running regular fuel and changing out the filter and draining off water every few months. This issue appears to be new since I replaced the tank. Did that in late september and drove 5 to 6k since then no issues.

Any ideas on how to clean the tube that runs from base of fuel bowl to T Valve at front of engine that is used to drain water off fuel bowl. The T valve does not work fuel wont come out I assume that white stuff filled the intitial hole that runs from base of bowl to T valve. Ca I run a wire down the T valve right back to the bowl? What is best wire size if yes? Is there a solvent I can run through?

Rags
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Old 11-17-2015, 09:43 AM   #7 (permalink)
Freddyack
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Quote:
Originally Posted by RagsNB View Post
Any ideas on how to clean the tube that runs from base of fuel bowl to T Valve at front of engine that is used to drain water off fuel bowl. The T valve does not work fuel wont come out I assume that white stuff filled the intitial hole that runs from base of bowl to T valve. Ca I run a wire down the T valve right back to the bowl? What is best wire size if yes? Is there a solvent I can run through?

Rags
Replace the line with 1/4" ID diesel rated fuel line. Attach the new line to the old and pull the new line through.
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Old 11-17-2015, 10:33 AM   #8 (permalink)
JMJNet
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I think that was there in the fuel line before.

x2 in changing all the fuel lines.

The line from tank is 3/8" and after the FFM is 1/4" as Freddy said.
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Old 11-17-2015, 01:33 PM   #9 (permalink)
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Keeping Diesel Fuel Clean

Water is the Enemy of Diesel Engines
See "Soft Solids"

The Damages of Diesel in Cold Weather
See "Consequences of Soft Solids" and "Glycerin"
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