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Mike S.
Mike S., Chevy Mechanic
Category: Chevy
Satisfied Customers: 6793
Experience:  ASE Certified Master Technician
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No fuel pressure? Replaced pump and filter. If I take line

Customer Question

No fuel pressure ? Replaced pump and filter. If I take line loose from filter it pumps fuel when I turn key on and when I turn it over. But I show no pressure at fuel rail fitting. Runs if I dribble fuel into tbody ?
Submitted: 10 months ago.
Category: Chevy
Expert:  Mike S. replied 10 months ago.

Disconnect the fuel line at the fuel rail and just before the filter on the engine side, then using air pressure of about 30 psi, blow through the line and feel if the air is making it through and if so, try it now after hooking the lines back up. If the air doesn't make it through the line, replace the line or find and repair the clog, kink, etc.

Customer: replied 10 months ago.

Will do ! Seems like pressure is weak , hard to tell with no reading at rail.

Expert:  Mike S. replied 10 months ago.

Let me know if that don't fix it and if so remember to rate me well so I get the credit.

Customer: replied 10 months ago.

Blew line out was good. Went to hook my pressure gauge back up and noticed my Schrader valve in gauge was gone. Lol. Anyhoot got 59 lbs fuel pressure. And spark still won't start.

Customer: replied 10 months ago.

No codes !

Expert:  Mike S. replied 10 months ago.

Check if the spark plugs are gas fouled. Remove one and smell if it smells like gas.

If so, remove and clean or replace them all. usually carb cleaner works if they are still in good shape.

If they are ok, check the fuel injector fuse, then see if it will start for a few seconds with starting fluid. If so, it is probably an injector pulse missing. First make sure there is voltage to the fuel injectors with the key on run and start and if so check for a ground pulse while cranking at each injector. Other than that, it may be an internal engine problem such as a timing chain/belt.

Customer: replied 10 months ago.

Replaced plugs and cap and rotor they were fuel soaked and cap and rotor had tremendous buildup. Anyway this truck hasn't run in years. Draining out old fuel as we speak. Once I get some known good fuel in it. Gonna do some more checking. Where is inj fuse ? I did notice while ckecking fuses btsi fuse is blown and it blows when I replace it. Could this cause no start.

Expert:  Mike S. replied 10 months ago.

I'll look that up, give me a few moments.

Expert:  Mike S. replied 10 months ago.

The fuel injectors and the ignition are fed from the "ECM IGN" fuse.

Expert:  Mike S. replied 10 months ago.

That fuse is in the I/P fuse block along with the ENG fuse which feeds the camshaft sensor and some other sensors.

Expert:  Mike S. replied 10 months ago.

If they are just numbered they are fuse 10 and 5.

Expert:  Mike S. replied 10 months ago.

I believe that btsi fuse has to do with shifting out of park. But I will look.

Expert:  Mike S. replied 10 months ago.

Yeah, that is the shift interlock. can you shift out of park?

Customer: replied 10 months ago.

I can shift out of park fine. All fuses are good except btsi. How do I see if injectors are firing. It sputters like it wants to start when I turnbit over.

Expert:  Mike S. replied 10 months ago.

With a noid light while cranking. Disconnect the fuel injector and hook up the noid light and crank the engine. the noid light should flicker.

Customer: replied 10 months ago.

Not familiar with this system where is injector or injectors ? Have noid lights ! Just don't know where to check ?

Expert:  Mike S. replied 10 months ago.

First of all, while I see if I an find a picture or diagram, when you checked that "ECM IGN" fuse did you actually test it for voltage with a voltmeter or 12 volt test light or did you just look at the fuse to see if it was blown?

Expert:  Mike S. replied 10 months ago.

It appears to me that fuse has to be ok, cause it also feeds the ignition coil and you said the engine does start with dripping gas into it so it looks like the fuel injectors are under the intake manifold and hard to get to, so I don't know why you cannot check for an injector pulse on one of the fuel injector ground wires at the vcm (vehicle control module). Let me see where exactly tat is located.

Expert:  Mike S. replied 10 months ago.

Before I forget, here is the engine wiring diagram.

Expert:  Mike S. replied 10 months ago.

The vcm is mounted on the passenger side of the engine compartment. It appears to be up at the right front corner, under the hood.

Expert:  Mike S. replied 10 months ago.

Here is a diagram,

Expert:  Mike S. replied 10 months ago.

now the difficult part is figuring out how to hook up that noid light while keeping the necessary wires still connected to the vcm so it powers up.

Expert:  Mike S. replied 10 months ago.

Try leaving all of the wires hooked up to the vcm and backprobing, that is sticking something in very small and metal into the back of one of those fuel injector ground wire connectors and then hook up the noid light to it and then to ground and then crank the engine and see if the noid light flashes. I would first make sure it has voltage on that connector to make sure you do have good contact. You should be able to see the noid light light up first when the key is just turned to run before start. Or double-check with a voltmeter or 12 volt test light. Let e know if you have a problem.

Expert:  Mike S. replied 10 months ago.

You should be back though and check all of those fuses with a voltmeter or 12 volt test light cause the vcm could just have a bad fuse or no power to a fuse such as like when a fusible link burns up. Or a faulty ignition switch.

Expert:  Mike S. replied 10 months ago.

If you can find a wiring harness to and from that sequential fuel injection unit, you may be able to unplug and test it there. I don't think you can reach the fuel injection unit though unless you remove the upper intake manifold and I don't think you want to do that just now.

Expert:  Mike S. replied 10 months ago.

I would try a used vcm before I even removed the intake manifold. It shouldn't cost more than $50 or so for a used one.

Customer: replied 10 months ago.

Vcm ?

Expert:  Mike S. replied 10 months ago.

I told you back at 10:46am, vcm (vehicle control module).

Now, what about the other question I asked you?

Did you actually test it for voltage with a voltmeter or 12 volt test light or did you just look at the fuse to see if it was blown?

Customer: replied 10 months ago.

Weird vcm info just came thru late I didn't see it sorry. Checked fuses with test light will swap vcm and let u know how it works out. Thank you sir

Expert:  Mike S. replied 10 months ago.

You are welcome...so you have a spare vcm?

Customer: replied 10 months ago.

Had to order one will be here Friday. Will let you know his it goes. Will it require reprogramming ? Or just install ? Thanks again.

Expert:  Mike S. replied 10 months ago.

Where did you order it from?

Expert:  Mike S. replied 10 months ago.

You know there are 2 different 4.3l engines that were in those. The Knock Sensor module may have to be swapped over to the new vcm, it's located under a plate on the VCM and is retained by two Allen head screws.

When replacing the VCM, the new VCM will need to be programmed.

Expert:  Mike S. replied 10 months ago.

This shows how to replace that module if it does have one,

Expert:  Mike S. replied 10 months ago.

I don't have that procedure though. Did they ask you for your vin so they could program it before they shipped it out?

Customer: replied 10 months ago.

No just asked for Id number on mod.

Customer: replied 10 months ago.

Yeah canceled the one I had ordered. You got a source that can send me a preprogrammed one ?

Expert:  Mike S. replied 10 months ago.

First of all which 4.3 is this? You can tell if it's the original engine, then look at the 8h digit of the vin, then tell me what it is. Also, since you already know the number off the module, what is it? How much was you going to spend on that module and why couldn't they program t?

Customer: replied 10 months ago.

4.3 x 8th digit. Mod # ***** ccsc . $75. I live in a little town in the middle of nowhere yards here don't have the ability to repro.

Expert:  Mike S. replied 10 months ago.

Autozone has one for $136, I would ask them if they can program it, http://www.autozone.com/engine-management/engine-control-computer/chevrolet/s10-p-u-4wd/1997/6-cylinders-x-4-3l-sfi?filterByKeyWord=vcm&fromString=search

Why are you jumping to the conclusion that it needs a new vcm so quickly?

Customer: replied 10 months ago.

Sorry I thought that's where we were at together. I just pulled codes again just for giggles there is a couple codes for map which I assume was from me trying to start with. Intake tube off throttle body. But also has a p1351 ignition coil 1 and 4 control circuit high voltage. Going to back up go thruposts and make sure I covered everything.

Expert:  Mike S. replied 10 months ago.

What were the map sensor codes? Write them all down then clear them and read if any come back after you try to start it.

Expert:  Mike S. replied 10 months ago.

How can your scan tool say ignition coil 1 and 4? Isn't there just 1 coil?

Expert:  Mike S. replied 10 months ago.

how many volts do you have to the ignition coil pin wire with the key on run?

Customer: replied 10 months ago.

Will check when I can ! I shoved it outside. Lol got some other stuff to get caught up on. Hollar soon ! Thanks mike

Expert:  Mike S. replied 10 months ago.

Ok, that's fine.

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