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Kevin Bourcier
Kevin Bourcier,
Category: Chevy
Satisfied Customers: 117
Experience:  Owner/Technician at Max Air Mobile
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2005 duramax 3500, won't start without pumping primer

Customer Question

2005 duramax 3500, won't start without pumping primer one time while cranking. Truck has a lift pump, supposedly new high psi pump and injectors. It's not sucking air have clear lines before and after filter housing.
Submitted: 11 months ago.
Category: Chevy
Expert:  Daniel Wilson replied 11 months ago.

Hi my name is***** will be glad to help. Check the filter housing and bottom sensor for leaks and the lines as well for any leaks in the system. these are known for leaks at the filter housing and is likely why your pressure is bleeding off. Let me know

Customer: replied 11 months ago.
Filter housing is new. As well I bypassed the filter housing with inline filter and still would not start. It's confusing as I have installed aftermarket lift pump on frame so it has positive pressure supply to pump without having to pump primer
Expert:  Daniel Wilson replied 11 months ago.

Thanks for the update. Do you have any fault codes logged by chance? If fuel pressure is good and no leaks the problem is likely electrical.

Customer: replied 11 months ago.
Only code is low frp while cranking. Once started by pumping primer just once, you can command frp to 160mpa and it will Maintain. It just won't build fuel pressure while cranking without pressing the primer, the lift pump pressurize to 8lbs so I don't understand why pressing the primer makes a difference.
Customer: replied 11 months ago.
Any other advise ?
Expert:  Gary replied 11 months ago.

Hi there,

Does your low pressure lift pump have an internal non-return valve?

If not I would add an inline non-return valve.

Gary

Customer: replied 11 months ago.
it's a non return pump, I even went as far as blocking the return to tank off to see if it will crank and run on its own, but it wouldn't. Still have to hit the primer just once while cranking and it will fire right up. I have pulled fprv out of pump and looks good and clean.
Customer: replied 11 months ago.
clear house before and after filter housing - no air
Expert:  Gary replied 11 months ago.

How about key on and off 5 times prior to starting?

5 seconds on 5 seconds off 5 times, like after changing a fuel filter.

Customer: replied 11 months ago.
It doesn't help any, it's just like the hpfp needs a small boost of fuel to start sucking it in to build the high pressure. I'm stumped.
Expert:  Gary replied 11 months ago.

I feel your pain.

You say it has a new high pressure pump?

New or original control valve?

Can you tee in a fuel pressure gauge near the filter the check the supply pressure?

Gary

Customer: replied 11 months ago.
Supposedly" it's new and so are the injectors. It looks like it has been changed, but just going off customer info. I have 8 lbs from the lift pump, it's a low pressure high volume. The fuel pressure regulator I assume came with the pump.
Customer: replied 11 months ago.
Any other help?
Expert:  Gary replied 11 months ago.

Hi again,

So somebody else has fitted a high pressure pump and injectors, has all the necessary programming been done?

Do you have a scan tool that can monitor rail pressure?

What happens to the fuel pressure gauge when you press the primer?

I don't think that 8 psi is enough.

Gary

Customer: replied 11 months ago.
I have snap on verus, I can do relearns, well they had 0psi from the factory so now it has 8 more,
So that should be a benefit and be as much psi and primer puts out.
Expert:  Gary replied 11 months ago.

It does sound baffling, the only thing I can now offer is a GM scan tool needs to be used, since possibly the learn functions aren't quite correct.

This is the original fault of no start unless the primer is operated?

Is the primer soft initially, and how much does it take to go hard?

And does it only take one pump on the primer, and the engine starts normally?

Gary

Customer: replied 11 months ago.
I have replaced many pumps and not had to use a scan tool for vehicle to operate. Just one pump and it starts. Primer is soft.
Expert:  Gary replied 11 months ago.

One more thing, perhaps the fuel tank is not venting well?

Can we take the tank cap off to see if that makes a difference?

Does it still have the intank pump?

Gary

Customer: replied 11 months ago.
I don't think you are familiar with the duramax trucks. They never had a low pressure fuel pump. And I ran a hose straight into a fuel can. I really would like to talk to a duramax tech I wonder if Maybe a common issue.
Expert:  Gary replied 11 months ago.

I'll admit that I'm not familiar with yours, but it does seem similar to some of ours.

I did think some ideas may help you.

I'm sorry I was not able to help you fix this, so I'll opt now, hopefully another tech with some specific experience will be along shortly.

No need to answer back as it will bounce the question back to me.

Hope you can fix this one.

Gary

Expert:  sprinkles08 replied 11 months ago.

Hello and welcome to JustAnswer!

Do you still need help?

Customer: replied 11 months ago.
Yea I do
Expert:  sprinkles08 replied 11 months ago.

What is rail pressure while cranking when it won't start?

Customer: replied 11 months ago.
I don't remember exactly, I know it's very low, I'll have to put a few things back together on it I tore it down to pull out fprv to check for debris or rust and didn't find anything. I'll check it Tuesday when I get back to shop and let you know. I want to say less than 500psi until you bump the primer once and it starts right up. Just doesn't make sense being that it has a lift pump to create the pressure without need of primer.
Expert:  sprinkles08 replied 11 months ago.

Let me know what you find and we'll go from there.

Expert:  Kevin Bourcier replied 11 months ago.

hello can I assist you ?

Customer: replied 11 months ago.
I'm supposed to be getting back with frp while cranking, it will be a couple days before I can
Expert:  Kevin Bourcier replied 11 months ago.

can I offer you a suggestion ? You say that the engine will always start after you pump the primer , correct ?

Customer: replied 11 months ago.
all it takes is one pump and it will fire right up, I have installed an aftermarket high volume low psi lift pump as well so there isn't a lack of fuel issue, I have replaced the fuel lines on engine with clear hoses and no air is present as well
Expert:  Kevin Bourcier replied 11 months ago.

once it starts . it runs fine , no problems ? and will it continue to start on its own if you turn it off and attempt to start it again ?

Customer: replied 11 months ago.
I haven't had it go into limp mode under heavy load, and frp will match desired when commanded to the highest. BUT it won't start back after it has started if you wait longer than 30 seconds or so. Then you have either hit the primer and very quickly crank it or have someone in the truck crank it while you press primer.
Customer: replied 11 months ago.
Could bad suction valve in hpfp cause this and sill obtain max rail psi?
Expert:  Kevin Bourcier replied 11 months ago.

okay so , humour me here if you can . Do you have access to compressed air ?

Customer: replied 11 months ago.
Yea
Expert:  Kevin Bourcier replied 11 months ago.

do you have someone there to help you ? Take an air hose with a blower nozzle , using a rag wrapped around the blower to form a " gasket " if you will . Apply a small amount of air pressure to the fuel tank at the fuel filler . With the air pressure applied ( do not apply too much , don't blow up the tank , LOL ) with the tank pressurized try to start the engine . Does it start ?

Customer: replied 11 months ago.
I tried that before I did anything to it and it did not help
Expert:  Kevin Bourcier replied 11 months ago.

okay . just checking . May I ask ? can you try it again please ?

Customer: replied 11 months ago.
Yea, but it will be next week before I can and I'll let you know. It shouldn't create much more pressure than the lift pump is sending to the hpfp.
Expert:  Kevin Bourcier replied 11 months ago.

bear with me . when you have the chance , try it again . :-)

Customer: replied 11 months ago.
Ok, thanks for the help, I'll update probably Tuesday after holiday when I get back to the truck.
Expert:  Kevin Bourcier replied 11 months ago.

okay . I am happy to offer my thoughts and hope that I can help get you fixed up .