Injectors Dripping, Not Spraying

chevrolet
s-10

#1

I am working on a 1991 Chevrolet S10 2.8L, TBI fuel injection.
It has sat about a year without starting, and now it will not run.
When I am cranking the engine, there is no spray from the injectors, only dripping. Roughly 1 drop per second. I believe I should see spraying.
Is that because the injectors don’t get enough fuel pressure? What is the most likely cause?


#2

You should be seeing conical spray from the injectors.

If you don’t see that, either the fuel pressure is too low, or the injector is defective.

Tester


#3

It may not have enough pressure


#4

Mine is the dribble, like the one on the right.
Seeing that both injectors are doing it, fuel pressure seems more likely than being defective.
Just wondering, what is the most likely cause? Fuel pump pressure, bad fuel pressure regulator, clogged injector final filters, bad injector O-rings?
It is a pain to get a fuel pressure gauge between the fuel filter and the TBI. Is it acceptable to place it between the filter and the fuel pump?
Thanks.


#5

If you can adapt a fuel pressure test gauge in the fuel system it’s acceptable.

My fuel pressure test gauge has every type of adapter to tap into the fuel systems.

Tester


#6

I tested the fuel pressure today, and I am getting about 1 psi, which is way too low of course.
The fuel pump runs, I can hear it, in fact I ran it manually from the prime connector.
I also had a problem with the loaner fuel tester - if I make the schrader valve finger tight, the valve is closed and the gauge is not getting any pressure. I had to open the knurled nut a bit before the valve would open, at which point a little gas would also leak out. I have never encountered this before. Maybe somebody really cranked down on this nut in the past and damaged something. Tomorrow I will get another tester, however I am 98% certain that the pressure is indeed low.
I also noticed some sparking as I touched the prop rod to the hood. I think the truck might have ground problems. Could this create problems for the fuel pump? I wish there was an easy way to check voltage right at the pump.
I did perform the sanity check of pouring a bit of gasoline down the throttle body and the truck ran for a few seconds.

So if the electric pump in the tank runs, but no pressure, can it be something like a stopped up pump inlet filter in the tank? Or bad pump ground? I did not notice any fuel leaks on any fuel lines, but I will look closer.


#7

If you can hear the pump and there is no pressure it is likely that the pump has failed or the hose connected to the pump inside the tank is leaking as mentioned in the other thread. Old fuel will damage fuel pumps and hoses.

While measuring the fuel pressure briefly pinch the fuel return hose with hose pinch pliers to see if the pressure builds, that with show if the the regulator is not holding pressure.


#8

I failed to mention, I terminated the fuel line at the gauge, so as to take the regulator out of the picture.

Would a low voltage at the pump cause low pressure, or is it unlikely?


#9

Low voltage would make the pump not run. If it’s running it should develop more pressure than 1 PSI.


#10

You guys were right. The rubber hose inside the fuel tank had ruptured. It was in a very bad shape, all soft, and kind of crumbling. What makes it deteriorate like that? The rubber fuel lines external to the tank seem to be ok.

I replaced the hose and the fuel pump. Now I have 13.5 psi between the pump and the filter, I figure it is about 13 psi at the throttle body, just about perfect.

Thanks.


#11

26 year old vehicle and ethanol fuel.


#12

One sanity check when I have fuel problems is just remove the fuel hose near where it connects to the fuel injection system input, set up a good sized container/hoses/etc to catch any fuel flow, and run the starter a few seconds while watching how much gasoline flows in that line. When everything is working, there is usually quite a sizeable flow out of that hose . Maybe a cup in 15 seconds of cranking, something like that. This test involves fuel-in-the-wild so can be dangerous of course, so make sure to do it away from any other cars or buildings, there are no open flames/sparks, and you have a sizeable fire extinguisher on hand. At one time I owned a CIS fuel injected VW Rabbit, so I have more experience on this topic than I’d really would have liked … lol .

Oh, forgot to ask, OP, is it running now?


#13

It is running now.


#14

Yup…Ethanol does a nice number to the interiors of older cars that weren’t designed to deal with a constant amount of E10 fuel. Not great for lawn mowers either…I’m lucky, though, there’s a gas station a few miles from my house that sells pure gasoline that I use for my lawn mower


#15

Next problem- You better figure out why it sparks from hood prop to hood. Check chassis ground connection…