[Solved] 1988 GMC Sierra - No Start

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Here is a list of tools I use every day at the shop. Let me know if you use them too in the comments!

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Customer Complaint:

This 1988 GMC Sierra was towed in with a no start condition. It belonged to the customer’s father, but has been sitting for a long time. The customer wants it to run again.

First Thoughts:

I like these old trucks and they are fairly simple to work on. The problem, though, is that a vehicle that has been sitting for long period of time could have multiple problems. We will see from this case study that the truck probably had one issue when it was parked, but developed more issues as it sat.

Diagnostics:

I was actually assisting another mechanic with this truck.

The other mechanic found that the vehicle would crank over very easily, had spark, and had injector pulse.

The other mechanic said he does not hear the fuel pump running, so we decided to use an alternative fuel to see if it would start.

In this case, we use starting fluid.

And as we expected, the truck fired right up.

This trucked needed a fuel pump!

The other mechanic installed a new fuel pump, a new fuel filter, and new gas. (There was old gas in the tank from sitting so long)

When the mechanic started to crank the engine, it still would not start.

We could hear the fuel pump running, we knew it had good gas and a clean fuel filter, what could be the problem?

This is a great example of what happens when vehicles sit for a long period of time.

We looked into the throttle body and it was dry.

The injectors were not opening and releasing any fuel.

I decided to measure the amperage on each injector.

Amp clamp attached to a fuel injector

After seeing the amperage of each injector, it was clear that the injectors were either shorted or stuck from being closed for so long.

Bad fuel injector amp ramp

Good fuel injector amp ramp

An injector amp ramp is supposed to be a ramp like the one above. When injector amp ramps are go straight up, then they are more than likely shorted.

After a new set of injectors, the truck ramp perfectly. Fixed!

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