Chevy Kodiak dumptruck gasoline problems

Except if you look at the pictures it has no carb - so no float, and no accellerator pump.

Except it has no carb.

You don't have a carb.

How do they work, do they create pressure, or are they just valves, with the pressure created by the in-tank pump?

A fuel injector is just a solenoid actuated spray nozzle. The in-tank pump provides the fuel pressure and the pressure regulator regulates that pressure sending excess fuel back to the tank via the return line.

On 2/14/2012 9:05 PM, snipped-for-privacy@snyder.on.ca wrote: ...

Yeah, the age got me thinking later and so I went and did look--it is, as I now see others have also noted (including you :) ) the TBI system.

I have already posted to Iggy to forget about what had said and the difference...

OK, now I have the picture, I think. I am now thinking of proper ways to troubleshoot this.

I guess that a first test would be to activate the fuel pump without cranking (by turning the ignirion key almost to the crank position), and apply 12v to the injectors.

Depending on whether they spray fuel or not, I will know what is wrong or at least will move in the right direction.

Thanks

To be kind to the injector coils I'd only apply full 12V to the injectors for a second or so. Normally injector drive circuits limit the current or PWM after the injector opens.

I probably would just check for the presence of voltage at the injector coil during cranking.

Eliminates pretty much everything but clogged injector.

OK, now the 64,000 dollar question: can they be un-clogged?

IIRC at least some are low side driven. They have +12 supplied all the time and the injector is opened by taking the other coil pin to ground. But you're right, no +12 will mean no fuel.

I would think soaking them in fresh gasoline should probably do the trick

Thinking you should still see *something* if you were to place the voltmeter in parallel with the coil...might not be anywhere near to a full 12 volts because of the pwm duty cycle but...

Pete, thanks, I have downloaded it and I am studying it.

Do you think that I should try to clean them in an ultrasonic cleaner?

If so, what liquid should I use for cleaning?

Also, if I need to clean them with ultrasound, should I submerge them completely?

If they are clogged they are pretty cheap. A quick search on Autozone has 1990 Chev TBI 7.4 injectors at $65ea.

Page 4-23 of the docs I scanned say that the fuel injectors should not be submerged in any type of liquid solvent or cleaner.

Should have looked at the pictures. That is NOT a carb. It is fuel injected. If you installed a pump for a carbed truck you have the wrong pump. If you installed the injected pump then you need to flush the injectors with cleaner.