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:

Cat 3126b losing prime. : I've used cat man before. my last…

Cat 3126b losing prime. ...

Cat 3126b losing prime.

Mechanic's Assistant: We'll do all we can to help. Tell me a bit more about what's going on so the Heavy Truck Mechanic can help you best.

I've used cat man before. my last problem was diagnosed as a shorted IAP sensor and haven't had any problems for 18 mos. then it just crapped out in basically the same way it did before an I'm unable to start.

Mechanic's Assistant: Is there anything else the Heavy Truck Mechanic should be aware of?

Nope. the suggestions thus far have been a bad fuel pressure regulator and or a bad fuel pump.

Show More
Show Less
Ask Your Own Medium and Heavy Trucks Question
Answered in 5 minutes by:
6/13/2016
Technician: Cat Man, Cat Engine Expert replied 6 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.There are two things I have seen cause a 3126 to lose prime.
The first and most common is a faulty fuel pressure regulator on the back of the head. I would replace this first.
Second is a faulty fuel transfer pump on the back of the heui pump.
Please reply back if you need more help or have more questions. I am happy to assist.
Ask Your Own Medium and Heavy Trucks Question
Customer reply replied 6 years ago
ok - as I'm broken down in my driveway, is this something that a roadside mechanic should be able to handle onsite? there's virtually no way of getting a towtruck in my driveway to get this RV towed out.
Technician: Cat Man, Cat Engine Expert replied 6 years ago
Oh yes. He should be able to take care of this onsite. Both of these parts are not difficult to change.
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
Customer reply replied 6 years ago
I am having a new fuel pressure regulator installed today and am hoping that is the problem. Once installed, do you think it will take a shot of ether to get the system going first or should it crank up without such (provided this is the cure)? This has been an intermittent problem for me for some time now, with it being much more pronounced when the temperature is below 45 (it usually never occurs during warm temps). Would cold temps more likely cause the pressure regulator to "flare" so to speak? Once I got it running (usually with a shot of ether), it always ran fine. Also, given that the transfer pump appears to be gear-driven, would it be susceptible to outside temps? Thanks!
Technician: Cat Man, Cat Engine Expert replied 6 years ago
No you should not need ether to start. Ether does help but not always necessary.
Yes temps can cause a difference. Normally colder is more the problem than when hot.
Let me know how you make out.
Ask Your Own Medium and Heavy Trucks Question
Customer reply replied 6 years ago
It took some ether to get it started after we installed the new fuel pressure regulator (I assume because there was a lot of air in the line and perhaps was air locked). It's started up each time just fine since then with no assistance. I guess the real test for me will be once it gets cold again this fall and winter. Thanks again for the advice & guidance.
Technician: Cat Man, Cat Engine Expert replied 6 years ago
Thanks for the update. Sounds like you got it fixed. That's great to hear. I'm glad you got it taken care of. Good job.
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
I have a 3126B Marine engine 3GS01197 AR 164-7858. The
I have a 3126B Marine engine 3GS01197 AR(###) ###-#### The engine started and ran rough for about 15 seconds then shut down. I suspect the fuel pressure regulator. I removed the regulator yesterday to… read more
Gary A.
Gary A.
Associates in Diesel Technology and Business Management
8 satisfied customers
I have a 1999 Sterling l85 11 plow truck with a cat 3126b
Good morning I have a 1999 Sterling l85 11 plow truck with a cat 3126b hasn't been drove much in the last few years started it a few months ago started good went to move it the other day it's been sit… read more
Gary A.
Gary A.
Associates in Diesel Technology and Business Management
8 satisfied customers
I have an fl80 3126B and it has no power nobody seems to
I have an fl80 3126B and it has no power nobody seems to find the problem. Everyday in the am when I go to work truck work ok but as soon as the truck gets to normal temp 180-200 it losses all power I… read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
I have a 2002 f750 with a 3126e cat ser #ckm35557, have had
I have a 2002 f750 with a 3126e cat ser #ckm35557, have had this truck for one year, I have put all new fulids and filters at the start of winter plowed for a totaled 84 hrs this season with no probbl… read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
I have a 99 3126b that after reaching operating operating
I have a 99 3126b that after reaching operating operating temp, with good oil psi, after sitting 15 min. cranks hard to restart. I've replaced the low psi oil pump (Got great psi after that), fuel fil… read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
FOR CAT MAN ONLY PLEASE! DO NOT ANSWER IF NOT CAT MAN. I
FOR CAT MAN ONLY PLEASE! DO NOT ANSWER IF NOT CAT MAN. I have a 2000 F-650 pickup with a CAT 3126b in it. Approximately 3000 hours of idling time and drive time combined with only 51k miles on it. Got… read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
Have a 3176 cat wont keep prime if it sit too. 9ck14146
have a 3176 cat wont keep prime if it sit too long … read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
UNIT EQUIPPED WITH A C7. TRUCK IS HARD STARTING/LOSING
UNIT EQUIPPED WITH A C7. TRUCK IS HARD STARTING/LOSING PRIME. IF YOU PRIME ENGINE AND GET IT STARTED, TRUCK RUNS FINE WITH NO ISSUES. LET UNIT SIT OVERNIGHT AND IT WILL LOSE PRIME AGAIN. NO SIGNS OF E… read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
I have a Cat 3126B with power loss/missing issue. When it
I have a Cat 3126B with power loss/missing issue. When it started it would miss then blow some blue smoke under load like climbing a grade or accelerating after a stop. They scanned it and foundcodes … read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
I have a 2001 cat 3126 ser no. 8yl74019 Starts fine runs
I have a 2001 cat 3126 ser no. 8yl74019 Starts fine runs great until up to Temperature,then will stall in will not restart without ether Then when it does start You have to use You have to keep foot o… read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
I need to talk with the cat man got a c7 with running
I need to talk with the cat man got a c7 with running problems … read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
Cat Man, Can you give me some spec on a cat fuel pump
Hello Cat Man,Can you give me some spec on a cat fuel pump(###) ###-#### What is the gph on it, and at what psi.… read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
Is there a Caterpillar engine expert available? We can't
Is there a Caterpillar engine expert available? We can't start a Cat 3126 engine in a motor home.… read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
Mr Cat Man, Long time no talk. I have a cat 3126B ESN:8YL92243
Mr Cat Man, Long time no talk. I have a cat 3126B ESN:8YL92243 that seems to be loosing prime. Can you tell me what is the most common problems you may see with this engine loosing prime. I appreciate… read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 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 am trying to diagnose a 2005 f-750 with a cat C-7 i have
i am trying to diagnose a 2005 f-750 with a cat C-7 i have replaced the IAP sensor all of the injectors report back ok with a cutout test i cant see a any abnormal amounts of oil leaking/squirting fro… read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
Mr. Cat Man, I Have a C7 esn:SAP10990 with code 164-11. I
Mr. Cat Man, I Have a C7 esn:SAP10990 with code 164-11. I have changed the IAP sensor and still with et my actual IAP is 400-600psi high than my desired iap. I noticed that all my injectors all squirt… read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
10,344 satisfied customers
Hi Cat Man, Iam working on a 1999 Peterbilt 379 with a 3406E
Hi Cat Man, I'am working on a 1999 Peterbilt 379 with a 3406E CAT in it, after sitting for a couple of days it will start up right away like usual but after about 10 seconds it will stall out.To get i… 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