GM

GM Repair Problems? Ask GM Repair Expert Now.

Ask an Expert,
Get an Answer ASAP!

GM
This answer was rated:

94 GMC: jump..Fuel pump, fuel injector assembly..fuel filter..No leaks

94 GMC JIMMY- Fuel Pressure Description...
94 GMC JIMMY- Fuel Pressure

Description: After two seconds of turning key fuel builds up to 54 lbs then when relay kicks out pressure drops to 10 lbs. Will not crank during cold weather sitting overnight, it will crank and run fine after using a jump booster for battery and cycling fuel pump relay several times.

History: Fuel pump, fuel injector assembly, fuel pump relay, fuel pump and sock, and fuel filter are new and have been installed within last two weeks. No leaks detected on any fuel line.
Show More
Show Less
Ask Your Own GM Question
Answered in 2 minutes by:
12/13/2010
Pete
Pete, GMC Technician
Category: GM
Satisfied Customers: 30,483
Experience: 14 years GM dealership technician and training.
Verified
Hello,I will be glad to try and assist you with this,Welcome to Just Answer.

Hi.

I just need a little more info to assist better.

When you replace the fuel injector unit was this the entire unit with the fuel pressure regulator attached?

Also when it does start does it run rough or rich at all at first?

Have you had the battery,alternator or draw tested for the battery concern?

Let me know so we can continue,Thanks Pete!
Ask Your Own GM Question
Customer reply replied 7 years ago
When you replace the fuel injector unit was this the entire unit with the fuel pressure regulator attached? Yes

Also when it does start does it run rough or rich at all at first? Runs smooth

Have you had the battery,alternator or draw tested for the battery concern? New Battery full charge and amps, 14.5 Volts from alternator.
O.k.

First to test to see why and where the fuel pressure is dropping of at there should be two rubber hoses in between the metal fuel feed and return lines under the vehicle near the frame rail on the drivers side up front,pressurize the fuel system then before the pump stops running clamp both of these fuel feed and return lines,if your fuel pressure drops then the drop is up front in the engine area.The most common cause is the fuel injector unit but another very common cause in the engine for the fuel pressure to drop is the nylon/plastic fuel lines that go into the fuel injector unit,these crack and can leak fuel into the engine especially when removing them to install a new injector unit,this is when they usually crack the most.

These become very brittle after years of use and I have made it a practice to replace these short lines under the upper intake when replacing the fuel injector unit.One way you can tell if this is the leak down for sure is by removing the upper intake and turning the key on to prime the pump,then look to see if these lines are leaking down the fuel pressure,most likely they are and need replaced.You can get these lines for around $50.These are very common to leak out the pressure.

if you clamp the hoses and the pressure does not drop then the leak down of the fuel pressure is in the tank and is the fuel pump check valve,even if the pump has been replaced you may have gotten a faulty fuel pump and it may need replaced again,the parts warranty will cover giving you a new part in exchange for this one.


As for the battery we know the battery tests good and is new and the alternator is charging so this only leaves a draw on the battery system.You will have to disconnect the negative cable from the battery,hook e multimeter in between the negative cable and the negative post on the battery,then turn the meter on to the amp scale and read how many amps the vehicle is drawing with all doors closed and the hood light off.If it is above 30 or 40 milliamps then you have a draw that is draining the battery down over night.Then you can pull each fuse one at a time to locate which circuit the draw is on,once the milliamp reading drops on one particular fuse this is the circuit at fault,then it can be determined what is on this circuit and each component on this circuit unplugged until the draw is found,then that component repaired or replaced.

Let me know if you need anything else,click accept if you feel satisfied with your answer as this is how I get credited for my time,Thanks Pete!
Ask Your Own GM Question
Customer reply replied 7 years ago

What is the best way to check pressure aft of the clamped hoses? If the pressure does not drop for the fuel injector assbly then release clamp and look for a pressure drop or connect pressure gage to fuel line near fuel filter? Fuel pump is an Airtex (auto zone special), original equipment was a Carter.

Air tex is a good design for the fuel pump but can be faulty in some cases.

You should have a fuel pressure test port on the engine at the back of the upper intake,test the pressure here.

Clamp the lines when testing fuel pressure here,then if it drops still then the leak is under the upper intake and remove the intake for inspection,prime the pump and see where it is leaking from.

Let me know if you need anything else,click accept if you feel satisfied with your answer as this is how I get credited for my time,Thanks Pete!
Pete
Pete, GMC Technician
Category: GM
Satisfied Customers: 30,483
Experience: 14 years GM dealership technician and training.
Verified
Pete and 87 other GM Specialists are ready to help you
Ask your own question now
Customer reply replied 7 years ago

Thanks Pete,

We will use your procedure, if we cannot locate the problem we will get back to you.

 

Happy holidays,

 

Leon

 

Sounds good,let me know what you come up with,happy holidays to you as well.

Thanks Pete!
Ask Your Own GM Question
Ask Pete Your Own Question
Pete
Pete
Pete, GMC Technician
Category: GM
Satisfied Customers: 30,483
30,483 Satisfied Customers
Experience: 14 years GM dealership technician and training.

Pete is online now

A new question is answered every 9 seconds

How JustAnswer works:

  • Ask an ExpertExperts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional AnswerVia email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction GuaranteeRate the answer you receive.

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:

I was having a terrible problem with the wheel bearings on my 98 Chevy Cavalier and I suspect that using this website saved me plenty of time and money.

Todd LRochester NY

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

< Previous | Next >

Meet the Experts:

GM Tech (Cam)

GM Tech (Cam)

GMC Mechanic

5,792 satisfied customers

GM Grand Master Technician 2007. 14 years experience.

Gary

Gary

GMC Technician

1,537 satisfied customers

15 years gm master tech/15 years ASE master tech

car tech

car tech

ASE Certified Technician

449 satisfied customers

25 year master tech and shop owner

Chris (aka- Moose)

Chris (aka- Moose)

GMC Technician

211 satisfied customers

16 years of experience

Paul M ASE Master

Paul M ASE Master

ASE Master Tech

187 satisfied customers

ASE Master Tech 20+ Years

Anthony

Anthony

GMC Technician

489 satisfied customers

GM Certified

Amedee

Amedee

GMC Technician

455 satisfied customers

ASE certified tech with advanced level specialist. Wisconsin certified emissions state inspector

< Previous | Next >

Related GM Questions
My 2011 Acadia vibrates when i accelerate. Original trans.
I had the motor mounts replaced, struts, and all ball joints at Midas. I replaced the axels 2 years ago. … read more
Dan
Dan
Automotive Technician
Vocational, Technical or Trade Scho
25 satisfied customers
I need to know where the wire goes from the starter to the
I need to know where the wire goes from the starter to the key switch because it's not getting all 12v to start the truck … read more
AutoDoc
AutoDoc
Shop Owner
Bachelor's Degree
1 satisfied customers
2003 H2 hummer starts and dies several times and then will
2003 H2 hummer starts and dies several times and then will start … read more
rpmdiag
rpmdiag
High school
7,274 satisfied customers
Trying to determine if my 2012 GMC Yukon Denali is an all
Trying to determine if my 2012 GMC Yukon Denali is an all wheel drive and if I need chains for snow driving. If I do, what size chains? … read more
Dan
Dan
Automotive Technician
Vocational, Technical or Trade Scho
25 satisfied customers
2015 Cadillac Escalade ESV, I accidentally let the iPhone
2015 Cadillac Escalade ESV, I accidentally let the iPhone charging cable touch the water that is salty on the floor of the drivers foot area and I think it blew the fuse. Where would I locate this fus… read more
GM Tech (Cam)
GM Tech (Cam)
GMC Mechanic
Vocational, Technical or Trade Scho
5,792 satisfied customers
Lose electric power when I us the plow. I'm thinking a bad
Lose electric power when I us the plow. I'm thinking a bad ground somewhere … read more
Chris (aka- Moose)
Chris (aka- Moose)
GMC Technician
Vocational, Technical or Trade School
211 satisfied customers
My 2001 GMC Sierra 4x4 with a 5.3 l motor starts and then
My 2001 GMC Sierra 4x4 with a 5.3 l motor starts and then immediately revs so high I have to shut it dow. … read more
David Craig
David Craig
OWNER/MECHANIC
Associates
4,410 satisfied customers
It cranks but won't start. Its getting fire but won't get no
yes its getting fire but won't get no connection..fuel supply working fine … read more
Gary
Gary
GMC Technician
Vocational, Technical or Trade Scho
1,537 satisfied customers
Hummer 2008 h3, cold weather 5 degrees, turn key on, all
Hummer 2008 h3, cold weather 5 degrees, turn key on, all lights come on and ready to start but turn key to start engine, eginee light stays on and i only here a click click click … read more
GM Tech (Cam)
GM Tech (Cam)
GMC Mechanic
Vocational, Technical or Trade Scho
5,792 satisfied customers
As I was driving along, the truck just died and will crank
As I was driving along, the truck just died and will crank but won't start … read more
GM Tech (Cam)
GM Tech (Cam)
GMC Mechanic
Vocational, Technical or Trade Scho
5,792 satisfied customers
I am installing a backup camera in my 2007 gmc 2500 and need
I am installing a backup camera in my 2007 gmc 2500 and need to know where to wire the monitor to the backup wiring in the cab … read more
Mechanic01
Mechanic01
1,703 satisfied customers
I just replaced the blower speed control for the second time
I just replaced the blower speed control for the second time in less than 6 months. I was testing the controls to be sure everything functions properly. As soon as I switch the to the face, the fan st… read more
GM Tech (Cam)
GM Tech (Cam)
GMC Mechanic
Vocational, Technical or Trade Scho
5,792 satisfied customers
06 hummer H2. Service 4WD. Switches flash when commanded. It
06 hummer H2. Service 4WD. Switches flash when commanded. … read more
Todd Audette
Todd Audette
Automotive Technician
Vocational High School
138 satisfied customers
My low beam lights will not turn on. Fuse is good and I have
fuse is good and I have used multiple bulbs, all have not turned on … read more
Todd Audette
Todd Audette
Automotive Technician
Vocational High School
138 satisfied customers
2005 avalanche and the car started and the emergency brake
2005 avalanche and the car started and the emergency brake light (brake was not pushed)came on and service 4 WD message. I shut the car off, unplugged positive side of battery for 5 minutes, cleared t… read more
GM Tech (Cam)
GM Tech (Cam)
GMC Mechanic
Vocational, Technical or Trade Scho
5,792 satisfied customers
My 2007 yukon denali just started today, the rear glass
Hello my 2007 yukon denali just started today, the rear glass access pops open and then the heated seats turn off, and the lights on the inside go dim, on and off. I shut the glass and when you hit th… read more
GM Tech (Cam)
GM Tech (Cam)
GMC Mechanic
Vocational, Technical or Trade Scho
5,792 satisfied customers
I have a Hummer H2 2003 model. I was running low on fuel and
Dave I have a Hummer H2 2003 model. I was running low on fuel and parked on hillside and believe fuel ran to front and uncovered fuel pickup. open door jumped out and left vechicle running and door op… read more
GM Tech (Cam)
GM Tech (Cam)
GMC Mechanic
Vocational, Technical or Trade Scho
5,792 satisfied customers
Smoke is comeing from my ac compressor.. 99 gmc jimmy. 4wd
Smoke is comeing from my ac compressor.. 99 gmc jimmy . 4wd v6 … read more
Mechanic01
Mechanic01
1,703 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.

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