Medium and Heavy Trucks

Have truck repair questions? Ask an Expert

Connect one-on-one with {0} who will answer your question

This answer was rated:

My cat 3126 won’t start. It’s a 2001 gmc t series truck with…

Hi my cat 3126...

Hi my cat 3126 won’t start

Mechanic's Assistant: What is the complete model and serial number of your machine?

It’s a 2001 gmc t series truck with a cat 3126 engine

Mechanic's Assistant: Are you fixing this yourself? What have you tried so far?

I have tried priming the fuel by pumping the manual pump it is cold out but my trucks webasto heater has been on

Show More
Show Less
Ask Your Own Medium and Heavy Trucks Question
Answered in 1 minute by:
1/29/2018
Technician: Cat Man, Cat Engine Expert replied 4 years ago
Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 10,344
Experience: I am ASE Master Truck Certified.
Verified
Thanks for asking your question. I will try and help you out.
Does the yellow check engine light come on when the key is turned to the on position?
Ask Your Own Medium and Heavy Trucks Question
Customer reply replied 4 years ago
A yellow “service engine soon” comes on and then goes off and a red “check gauges comes on
Technician: Cat Man, Cat Engine Expert replied 4 years ago
Thanks for the information.Since the yellow check engine light comes on, this indicates the engine ECM is receiving power and functioning. There are several things that can cause a crank no start on this engine.The first is a low or no fuel pressure condition. The engine needs at least 25 psi to start. If it is low, the injectors will not get filled and it will not start. If the engine has a hand priming pump, and it gets stiff when operating it, the engine has enough pressure to start. If there is no hand priming pump, I would connect a psi gauge and measure the pressure. If the pressure is low, I would change the fuel filters first if you haven’t already. If it is still low, I would suspect a failed fuel pressure regulator on the back of the head or a weak fuel transfer pump. The pump is located on the back of the HEUI pump.Second is a low injection actuation pressure. This is the high pressure oil system that activates the injectors. The engine needs at least 870 psi to start. If it is low, you have either a failed Injection actuation pressure control valve in the HEUI pump, a weak HEUI pump, a high pressure oil leak at an injector, or a faulty Injection actuation pressure sensor. To test the sensor, just unplug it. If the engine starts, the sensor is bad. It has 3 wires and is located on top of the engine near the front and screwed into the head.Third is a failed engine speed timing sensor. Your engine has two. They are located on the driver’s side of the engine on the back of the engines front cover under the HEUI pump. The bottom sensor is the primary start sensor. If it has failed, the engine will be hard to start. The top one is the primary run sensor. They come as a pair.Next is low battery voltage to the ECM while cranking. The ECM must have at least 7.5 volts DC to operate. I have seen weak batteries or a poor connection cause low voltage. You could have a poor connection at the batteries or starter.Next is a faulty engine ECM. The ECM has an injector driver module inside. This is what powers the injectors. If it fails, the ECM will log injector codes for all the injectors.Lastly are worn injectors. Over time the injectors can wear if they have a lot of hours on them. To verify, I like to check AC to the injectors while cranking. You should have between 20-40 AC while cranking. If you do, and you have good fuel pressure, the injectors are worn.Most often when these things are happening there will be diagnostic codes in the ECM. If your engine has cruise control switches, you can pull the codes. If you have never done this, let me know. I can get you the procedure.Please reply back if you need more help or have more questions. I am happy to assist.
Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 10,344
Experience: I am ASE Master Truck Certified.
Verified
Cat Man and 87 other Medium and Heavy Trucks Specialists are ready to help you
Ask your own question now
Technician: Cat Man, Cat Engine Expert replied 4 years ago
Phone call session started
Customer reply replied 4 years ago
How do I know which is the faulty Injection actuation pressure sensor?How do I know which is the faulty Injection actuation pressure sensor
Technician: Cat Man, Cat Engine Expert replied 4 years ago
It’s the one on top of the head near the front with three wires. It screws into the head.
Ask Your Own Medium and Heavy Trucks Question
Was this answer helpful?

How JustAnswer works

step-image
Describe your issueThe assistant will guide you
step-image
Chat 1:1 with a technicianLicensed Experts are available 24/7
step-image
100% satisfaction guaranteeGet all the answers you need
Ask Cat Man Your Own Question
Cat Man
Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 10,344
10,344 Satisfied Customers
Experience: I am ASE Master Truck Certified.

Cat Man is online now

Related Medium and Heavy Trucks Questions
Working on a 3126 cat in a 1998 Chevy 7500. Cranks no start.
Working on a 3126 cat in a 1998 Chevy 7500. Cranks no start. I have over 800psi icp pressure during cranking. Pulled plug on filter housing and fuel just trickling out. Fuel filter is full and priming… read more
Mike Mcmillan
Mike Mcmillan
Triage Tech/Shop Foreman
Associates
607 satisfied customers
Shut off engine and won't start in morning, in shop and
Shut off engine and won't start in morning, in shop and warm. No fuel getting as in shutdown switch or something … read more
Wayne
Wayne
Journeyman
Vocational, Technical or Trade Scho
5,115 satisfied customers
I have 99 gmc c6500 topkick with 3126 cat only start with
i have 99 gmc c6500 topkick with 3126 cat only start with starter fuel … read more
Mike Mcmillan
Mike Mcmillan
Triage Tech/Shop Foreman
Associates
607 satisfied customers
30 Celsius started truck ran for a few minutes and died,
30 Celsius started truck ran for a few minutes and died, thick summer fuel, tried new filters with fuel conditioner in them, still not starting … read more
Nich1019
Nich1019
Diesel Technician
Vocational, Technical or Trade School
80 satisfied customers
We have a 1996 Kenworth T300 with a Cat 3126. Short on power
We have a 1996 Kenworth T300 with a Cat 3126. Short on power and always cranks does not always fire. Yet will fire on either and continue to run. Replaced the fuel nd water separator filters. … read more
Joel Bos
Joel Bos
909 satisfied customers
Please only answer if you are an expert on the cat 3126
Hello Please only answer if you are an expert on the cat 3126 HEUI … read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
2001 gmc c7500 cat 3126 does it have electric fuel pump and
2001 gmc c7500 cat 3126 does it have electric fuel pump and where is it … read more
Mike Mcmillan
Mike Mcmillan
Triage Tech/Shop Foreman
Associates
607 satisfied customers
I have hard time starting my truck GMC 2001 w/cat 3126. 2001
I have hard time starting my truck GMC 2001 w/cat 3126 … read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
Got a 2001 gmc topkick with 3126 in it. Was running fine.
Got a 2001 gmc topkick with 3126 in it. Was running fine. Went to start long cranking. Had already run into bad inj actuation sensor couple weeks back. Fixed that. I unplugged the sensor again to test… read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
Cat Man 1999 Ford Sterling 3126 cat. Evidently lost fuel
Hi Cat Man 1999 Ford Sterling 3126 cat. Evidently lost fuel prime(even though 4" in tank) as the secondary filter was not full of fuel. hand primed until i had fuel coming out of the fitting opposite … read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
I am researching the reliability of a CAT 3126 engine. I
I am researching the reliability of a CAT 3126 engine. … read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
Having a problem with our 3126 equipped tow truck. It is in
Having a problem with our 3126 equipped tow truck. It is in a 2001 Chevy T7500. The issue is with the fuel pressure. It is having a problem where it looses fuel pressure under load. It was low on fuel… read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
I have a 1998 gmc top kick with a cat 3126 motor will not
I have a 1998 gmc top kick with a cat 3126 motor will not start unless I manually prime then runs and stalls after the primed fuel runs out sometimes stays running driving tell you take a corner or go… read more
FIX-IT
FIX-IT
Comercial transport technician
Vocational, Technical or Trade Scho
829 satisfied customers
I have a 3126 cat that I can pump up fuel pressure with hand
I have a 3126 cat that I can pump up fuel pressure with hand primer pump but will lose pressure if it is running or not?… read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
I have a 2000 gmc 8500 with a cat 3126 it has sat for about
I have a 2000 gmc 8500 with a cat 3126 it has sat for about two years I did start it from time to time I was driving it to get a state inspection and it drove fine for about three miles then it acted … read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
I have a 2005 chevy kodiac 7500 dump truck with an auto. transmission.
I have a 2005 chevy kodiac 7500 dump truck with an auto. transmission. The engine is a Cat. C7 #3126. One of my workers ran the truck out of fuel and I can not get it started. I have fuel at the water… read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
i have a 2002 Caterpillar engine model 3126 in a motorhome,
i have a 2002 Caterpillar engine model 3126 in a motorhome, how do i drain air in fuel line, or prime it?… read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
I am still having problems with my 3126 losing prime where
I am still having problems with my 3126 losing prime where is the lift pump located on the huie pump and do you have a picture of it. Is it hard to replace? I have a 02 6500 with a 3126 cat engine… read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

JustAnswer in the News:

Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.

What Customers are Saying:

Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help.

Mary C.Freshfield, Liverpool, UK

This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!!

AlexLos Angeles, CA

Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult.

GPHesperia, CA

I couldn't be more satisfied! This is the site I will always come to when I need a second opinion.

JustinKernersville, NC

Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around.

EstherWoodstock, NY

Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know.

RobinElkton, Maryland

He answered my question promptly and gave me accurate, detailed information. If all of your experts are half as good, you have a great thing going here.

DianeDallas, TX

< Previous | Next >

Meet the Experts:

Daniel Wilson

Daniel Wilson

6,062 satisfied customers

Owner at DJ Wilson

Cat Man

Cat Man

Cat Engine Expert

10,344 satisfied customers

I am ASE Master Truck Certified.

Wayne

Wayne

Journeyman

5,115 satisfied customers

worked on, Gmc, Macks, Freight liner,Mercedes Benz,,Ford, sterling

Jeremy

Jeremy

Certified Truck/Bus Technician

2,756 satisfied customers

ASE Med/HD Truck Technician, NATEF Diesel Engines and Electrical/Electronics Technician, Network Engineer specializing in CAN faults, Aftertertreatment, and vehicle communications

Curtis B.

Curtis B.

Technician

1,947 satisfied customers

Technician turned service manager on multiple lines of trucks and engines, used in industry.

cumminsdr

cumminsdr

Mechanic

1,886 satisfied customers

All types of Cummins applications

Chris (aka-Moose)

Chris (aka-Moose)

Technician

641 satisfied customers

24 years of experience diagnosing & repairing

< Previous | Next >

Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Show MoreShow Less

Ask Your Question

x