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Old 06-16-2015, 09:39 AM   #1
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Cat 3126 will not start... low High pressure

This may be a bit long, but maybe it will help someone else.

I had a problem starting my 2004 Fleetwood Discovery 39L. Freightliner Chassis, Cat 3126E engine. Would crank but would not start. I know nothing about diesels so called local heavy duty truck shop (MHC) for road call ($135 an hour).

Mechanic brought diagnostic program and after about an hour said it was low oil pressure (200 psi) coming from high pressure injector pump. Said he needed to go back to shop and order new one. Couple days later, they returned to install new pump. Did same thing and burnt up my starter in the process.

They wanted to charge me $400 for new starter plus installation fee. I ordered starter online and changed it myself. Still could not get motor to start so called them back out.

Software said still getting 200psi. He thought something was plugging up internal works so he dropped oil pan and worked on internal oil pump. Nothing wrong.

Came back two days later and did what should have been done the first time he came out.

This is what you need to do if you have similar "no start" problem.

If the diagnostic software gives a low psi reading, have them verify low oil pressure with a manual guage before changing the high pressure injector pump.

In my case, the engine oil pressure sensor was giving the ecm improper electrical value and the ecm was reading 236 psi oil pressure. The manual guage read 5000 psi. He changed the engine oil pressure sensor and the ecm started receiving the correct psi reading. Engine started then.

If he had checked the pressure with a manual guage before changing HUEI he would have found the sensor bad then. Total cost for me the way he did it was $3800. If he had checked pressure manually first.... maybe $3200 cheaper. The pump was not malfunctioning, thus the $1350 for rebuilt pump plus installation labor was uncalled for, along with dropping the oil pan and everything else he did. Lesson learned and hopefully I won't have this problem again.

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Old 06-16-2015, 09:46 AM   #2
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And find a new mechanic?

HR 29 fks TT, 1 slide, Chevy Silverado, RVM 167
Next stop?
Previous rigs..2 Pickup campers,2 TT's, 3 DP MH's
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Old 06-16-2015, 09:54 AM   #3
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When you full timing... you don't know anyone in the area.... you use people that are known nationwide. This guy came out with the idea that it was a simple fuel problem and he could "fix" it and go home. Had called around and one guy recommended MHC because he felt the Freightliner shop locally was worthless. So much for word of mouth.
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Old 06-16-2015, 09:58 AM   #4
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My only concern now is that other's have an idea of the steps that need to be taken before shelling out big bucks for an un needed HUEI. I had read many posts about a "no start" problem on this engine, but never saw the corrective action. Seems as though a lot of people will ask for advice until they get the problem solved, but will not post what actually corrected their problem.
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Old 06-16-2015, 03:05 PM   #5
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Thanks for sharing! Man is there no recourse for all the unneeded parts and labor? If all we are going to do is throw parts at the SOB I would do it myself! We hope that the pro's know what they are doing.
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Old 06-17-2015, 07:52 AM   #6
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Thanks for the follow-up, an so sorry that you were paying for the so-called-pro's eduction. There is often a big difference between "profesional", and "expert"; the former often being simply someone who gets to charge for his work, even though he may not know what he is doing.
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Old 06-17-2015, 08:32 PM   #7
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Here's a document , that may help , other owners with the no start condition , before a bunch of $$$ gets spent.
Disconnecting the high oil pressure sender will put the engine ECM, into default mode and if the engine starts , the sensor is the problem. Page 4.
Attached Files
File Type: pdf 3126B no start.pdf (130.3 KB, 180 views)
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.
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Old 06-17-2015, 08:40 PM   #8
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That's the trouble with a lot of "mechanics" nowadays! Just keep throwing parts at it (on the customers dime) till something fixes it, we'll just bill the customer for it.

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