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1994 Chevy K3500 6.5 diesel 4x4

retired09 said:
Thought fuel filter was leaking, it was main line from lift pump to fuel filter busted under clamp. Cut off inch and put line back on.
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Replace your fuel lines next chance you get. This includes the real fun IP to filter line, the fuel supply line and tank return line on back of engine. Also the IP line to the fuel return steel line. Your rubber lines are shot to break like that.
 
WarWagon said:
Replace your fuel lines next chance you get. This includes the real fun IP to filter line, the fuel supply line and tank return line on back of engine. Also the IP line to the fuel return steel line. Your rubber lines are shot to break like that.
Click to expand...

Might as well get a feed the beast kit.:D
 
buddy said:
You should check for the Optical Sensor Filter. If its there remove it. And then clear codes and run it.

It looks like this and will be plugged into the top of the IP. You want to remove it and then connect the engine harness straight to the top of the IP.
View attachment 15307
Click to expand...
Cleared codes after removing OSF and drove truck. Instead of codes 18 35 and 49, now have 17 18 35 43 and 49. Any other suggestions. JiFaire said remove filter and plug back together. Just unplugged filter from Ip and PMD is plugged into Ip. Thanks...
 
Grr... you are eliminating things left and right here... this is pointing to 3 possibilities... either your PMD/harness has a problem, or you have air getting into your fuel, or your IP is dying.

Let's start with the first one.. only do one thing at a time from here on in, so we can rule out some stuff. Oh, and you can probably put that OS filter back in... doesn't matter all that much, but if it isn't fried, it might as well be in there.

=====

You indicate that this issue started after you changed your PMD? You also indicate that the extension harness is home-made.

Tell us more about that... did you just cut/extend the existing harness? Crimp or solder? Or did you buy the end plugs and make a new one... does the problem disappear if you plug the PMD directly into the engine harness? It doesn't take much of a short in the IP wiring to cause you grief... either in the PMD harness or the OS harness; check every connection and wire you can find.

Air in fuel is tested by buying a couple feet of clear tubing and putting it in-line with your fuel line right before the IP... look for bubbles. Your fuel has to pass through an optic sensor; if it has bubbles it drives it crazy.

IP... let's not go there yet - except to answer my earlier question about lubricity additives? I put a quart of 30wt motor oil in every tank of ULSD diesel to keep my IP lubricated... my 17, 18, 35 codes went away when I did this.
 
retired09 said:
Cleared codes after removing OSF and drove truck. Instead of codes 18 35 and 49, now have 17 18 35 43 and 49. Any other suggestions. JiFaire said remove filter and plug back together. Just unplugged filter from Ip and PMD is plugged into Ip. Thanks...
Click to expand...

You cant just leave the top of the IP unplugged, that is worse. You need to plug the engine harness back into the top of the IP. So you removed the filter, but take the end the filter came off and plug it in.
 
I would have started with the sightglass(clear tubing on fuel line) 1st. always best to eleinmate that. These trucks are know for rotted fuel lines.
 
I just got off the phone with him a little bit ago, he's going after a vac/press gauge so we can do some proper diagnostics, sound like from description on phone he was/is losing fuel to the IP, he has found & corrected 1 issue with the supply line under the intake leaking , replaced it, going to pressure check the rest of the rubber lines that were not replaced, and test OPS/lift pump, and possible snotty sock. Also possibly a bad optic RFI filter, but we'll do basic stuff 1st
 
changed all fuel lines from tank to IP pump, that was fun. Put vacuum on lift pump, little to no vacuum. Oil pressure stays between 40 and 55 lbs. Can I wire new lift pump direct to ignition bypassing oil switch and not have to buy new oil switch? That switch is 110 dollars by itself. Remember I'm retired, lol Thanks
 
You can wire the LP to ignition, but what did you mean by you put vacuum on the lift pump? Are you saying there was no pressure when the truck was running? Thats why you believe the OPS is dead?

I dont know if you ever answered is the SES light coming on a new thing?

Have you tried removing the OS filter and plugging in the end you remove the filter from?
 
I wired my LP to the key but I did recieve a saftey lecture. Remember, if you are involved in an accident the LP will keep running as long as the key is on feeding any fires that may happen. I relaize this is a minor possiblity and I have wired a few without the OPS but you should know that.
 
Well guys, have changed all fuel lines from tank to IP. Installed new coolant temp. sensor few days ago. Installed new LP today and found that it had been wired to ignition by previous owner. Hooked OPS plug to LP plug without ignition wire and no power to LP. Spliced ignition wire to hot wire on LP and pump has power. Cleared codes and started truck. Still little hard to start but finally started. Reved engine to 3500 rpms and engine coughs . Eased back to 2500 rpms and running smooth. Had codes before installing LP of 18, 35, and 49. Turned off engine and now have codes 15, 18, and 49. Would buying new OPS and hooking it to LP like normal, fix anything? Bled all air from lines before starting truck . Could optic sensor be bad? Engine runs like timing off few degrees. Trans still not shifting into high gear. Fluid full and clean. Would changing speed control sensor help? About ready to drive this truck into lake, LOL. Help...Thanks P.S. Put qt. of 30 wt. oil in tank at fillup as advised.
 
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18...Pump cam Ref. pulse
35...Injector pulse width (short)
49... Service throttle light


15....Engine coolant temp (low temp)
18...Pump cam ref pulse
49... service throttle light

1) Ok, do you have the engine running when you are trying to get codes??? As stated before this will throw the 49 code in a heartbeat.

2) did you look at the wiring harness to the IP while you were changing the fuel lines??? It lays in the valley and can get heat damaged.

3) check the big wiring plugs in the back by the fuel filter housing make sure these are plugged in tight.

4) The low temp code will not let the convertor lockup and will run the engine at a higher idle until it taken care of. I know you changed the sensor already.

5) please check ALL the grounds. Batteries too. These first gen ECM's are very ground sensitive.
 
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