No start on 1996 suburban.

[handliner]

I have a 1996 suburban 350 4 wheel drive "R" that fails to start. If I cycle the key/fuel pump several times it still doesn't start, but can hear pump running. When I spray starting fluid thru intake it fires right up and runs. 157,000 miles and fuel pressure regulator was replaced about 50-100 miles ago, I replaced regulator because I thought it might be the problem. Anyone out there have any ideas? Fuel pressure will be tested this evening or sometime tomorrow. I also have purchased a new fuel pump but have not installed yet. No codes stored in computer.

Thanks in advance for any input.

Bryan

[ratmn218]

fuel pump most likely, pressure i think should be no lower than 52 psi.

[Jeremy airjer W]

The spec is 60-66 psi. I would like to see at least 58 psi. The reason you need the high pressure is because the poppets (the mechanical injector that sprays the fuel onto the back of the intake valve) only open at a certain psi and higher. If its to low the poppets will never open.

[handliner]

Had pressure tested this evening, 50-51 psi. How can it run after starting with starting fluid?

[Jeremy airjer W]

I've seen and heard of it more times than I can remember. The only thing I can figure is that once its started there is vacuum in the intake. Since the difference in pressure is greater, it requires less fuel pressure to operate the poppets after the vehicle is running. What do you think 4WE?

[Scott K]

I guess I dont know why, but I do know that 51 psi is to low and I know if it isnt atleast 57-58 psi they dont start. Your theory sounds good with the poppets, but I dont know. I could ask someone tomorrow, if I remember to.

[handliner]

Installed new fuel pump this morning, runs like a champ again. Thanks for the input.

[Scott K]

Glad you got it fixed!

[JollyT]

A theory, when the engine turns over, the voltage jumps up a volt or so from the alternator turning and increases fuel flow from the weak pump. This is just an idea that struck me.

[Jeremy airjer W]

I like that one too!

[Shack]

Not to beat a dead horse here, but when where you testing the fuel pressure?

Key on/eng. off, while cranking eng. over or after started with starting fluid and eng. at idle?

Maybe fuel pressure was fine after started???? Fuel pumps that are weak, do funny thing.

Air's idea I would say sounded the best

[Scott K]

Ok, to start the engine it needs a richer mixture so by adding the extra fuel (ether) it starts, the poppets inside the injector is a high pressure poppet and doesnt give a good spray pattern to get the rich mixture for start up with low fuel pressure, but is enough to run the vehicle once it is going.

[handliner]

Fuel pressure was tested both while trying to start the truck and when the truck was running.

[Jeremy airjer W]

I guess you could argue that the poor spray pattern has an easier time atomizing in a vacuum. Lower the pressure and lower the boiling point.