kthiemann

I know this is a Cummins site but thought I might throw this one out there for discussion.



I have a 03 Sterling with a cat 3126 sitting at the shop that is weird, if you leave the thing sit outside overnite when you start it it will run for maybe 10 minutes and then act like it runs out of fuel, but if it's left indoors it will start and run all day. No codes, replaced the fuel filters and the primary fuel filter was full while the secondary was left than half full, primed the secondary filter with the hand pump and it started and ran for a short time and died again and again the secondary filter was empty while the primary was full. Checked the fuel supply lines and they are clear with no restrictions. Did notice a slight fuel leak from the hand pump when cold so I replaced that thinking it was allowing it to suck air but that was no help. Am thinking the fuel pump mounted on the back of the HUEI pump is bad but am looking for any suggestions.

Thanks in advance for any thoughts anyone might have.

pevaguy

It sounds like it is sucking air somewhere between the primary and secondary filters. Check all the fittings, fuel line, and filter bases in that area. If it was before the primary, then both would be getting drained. If it was after the secondary, neither would be drained, so it would probably be between the two filters where the problem is.

1-5-3-6-2-4

fuel lines have been known to deteriorate the internal sleeve over time, and some places peel some back a flap and it creates a check valve effect. not all the time thought. '03 seems a little new for the problem though. but you never know.

Hvytrkmech

I would put a fuel pressure gauge in the loop just before the fuel pump. You should see at least 60psi steady, (from memory). If you have steady fuel pressure at the time the engine stalls then move on to the hpop. I am not sure if you can dead head the hpop with the laptop on the cat. That is how I do it on an Intertrashional. Look for engine start pressure on the hpop then wot pressure. I believe you should see around 900 psi for engine start and around 3000psi at wot.


If you do notice a drop in fuel pressure just before engine stall then look for any check valves in the fuel line system, inspect them first. If they are ok or if there are none, then inspect all fuel lines and connections,(see below). If the fuel lines are ok then suspect a fuel pump. When was the last time the oil was changed?

One more thing to consider on any engine with some mileage and age on it. After the switch over to ulsd a lot of problems with fuel line o-rings surfaced causing hard to diagnose fuel delivery problems. Check them if there are any in your system.

Even though you have no fuel line obstructions you may have one or several lines that have deteriorated and collapsed the inside rubber jacket or made the lining porous enough to ingest air without leaking fuel. I know it sounds strange, but I have encountered these issues with newer trucks than yours. Also look in the secondary fuel filter head for any obstructions, like fuel additive foils or such.


Let us know what you find.

kthiemann

Thank you for your suggestions, ya'll have given me some good food for thought, will look tomorrow and post back with what i find.

kthiemann

Looks like peva hit the nail on the head, this thing had hard plastic lines with compression fittings from the tank past the primary filter to the fuel pump on the back of the HUEI pump. Come to find out that the compression fitting on the back of the pump was missing the insert that keeps it straight and the compression sleeve was crooked by about the width of a human hair. Cut the end of the hose back just a hair and redid the compression fitting with all the proper pieces and at least this morning it worked perfectly, am gonna try it again tomorrow and see what happens. Thank you for the suggestions.

Riflemanusmc

C-7's have the same problem..Sorry for getting on this so late...

high bid

wow, we ran 3126TA....nothing but problems. One was rebuilt and then the other began blowing oil out the exhaust. Never again. Hope you have better luck.

wannadiesel

I'll have to look at that fitting on the one I drive at work. It will sometimes lose prime over the weekend, but the Davco stays full so I know it's up past the secondary somewhere.

kthiemann

I've got somewhere between 50 and 60 trucks with this stinkin engine in them that I have to take care of and am really learning to hate cat. drivability with a passion. I like working on the cummins trucks we have and really don't even mind the mercedes trucks (mostly cuz they are still under warranty) but these stupid cat trucks are a giant pain in the backside....

Riflemanusmc

Alot of them, we found the fuel inlet lines loose at the back of the pump....They didn't leak because they were on the suction side....Hope that helps...

wannadiesel

The one at work was damp and I got 1/4 turn on it very easily. I'll know tomorrow morning if that got it. If not I'll get a new ferrule and sleeve and trim the line. I never figured it had a suction side leak because the Davco stays mostly full.

The shop said it was injector o-rings...

Riflemanusmc

Did I do good???!!!LOL.Thats a fairly common problem with them..I found that one by outhouse luck. Had the tech throw air to the fuel tank. Found it then!

wannadiesel

Didn't got it. I cleaned it up real good yesterday and it's damp again. Ferrule and sleeve time...

It'll be nice to not need ether to get 'er lit after a 3 day weekend. I HATE doing that to the poor thing.

Riflemanusmc

Thats an easy cure..Crack in the plastic suction line from the tank.......C7 Cats had the same problem..I thought you were going to replace the ferrule and fitting????