My son is broke down about 30 miles from here, and I can't get away to work
on his truck. He had shut the truck off to run into a store and it would
not start after. Some coughing like it wanted to start, but no start. He
replaced the fuel filter as the pump was not pushing gas past the filter
(the pump was outputting fiercely), and now has fuel all the way up to the
engine. He hit the schrader valve a few times and gets a good flow of gas
now if he does that. He does not have a way to measure the fuel pressure at
that point though.
If he hits it with a can of starter fluid, the truck will start but stalls.
Will not start just off the fuel system. He just replaced the fuel pump a
couple of weeks ago, and like I said, he replaced the filter today.
Since I can't get down there, I'm sorta looking for ideas - things I might
have missed having him do.
Things to check on a Blazer (assuming the Vortec 4.3)...
1. Fuel injectors / spider unit. Could be clogged. Generally won't stop you
from starting, but worth a look. I think this can be checked with a code.
2. Starter - they are known to go bad and are located in the most obnoxious
place. I forget where.
3. EGR Valve - again if this is bad, you may be having a hard time getting
air into the system.
4. Air intake - sometimes these get clogged and can kill the engine before
it even gets a chance to fire.
Since the fuel pump was replaced, is it getting the right signals? Is the
I would run a code check and see what's being thrown.
All things point to the spider right now. I've discovered some common
failure ideosyncracies with the spider on these motors.
Nope - turns over very strong.
I had considered that, but I put this down further in the chain of likely
I dicsounted this (and EGR) since the truck will run off of starter fluid,
so it does breath. As well, it had just been driven into the parking lot,
and shut off of a quick run into the store. Less than 5 minutes later, back
in the truck, no start.
Yup - huge fuel spray out of the pump. Had him replace the filter roadside,
because he was only getting a dribble out of the filter. Sold delivery out
of the filter now, and out of the schrader valve up top. Good fuel delivery
all the way to the throttle body.
He just happened to have a code reader in the truck, because he was up here
the night before to replace shift solenoid 1-2 in the tranny. Plugged it in
and no codes. That's a big part of what prompted me to reach out here with
my original post.
Thanks for the reply...
Nope. It'd definitely a fuel delivery problem. Now appears to be a spider
issue. I've learned it's not uncommon at the age and mileage of this
vehicle (110,000 mi), that replacing the fuel pump will often blow out the
poppets on the spider. Sunday is the day for that exploration. Thanks for
That too seems to be a common experience. The originals seem to go quite a
ways, and then replacements seem to fail earlier. Looking around, it seems
that the MPI spider can be installed as a direct replacement for the CPI
spider. Appears to be a more robust spider and a better delivery system.
Any insight into this swap?
Mike Marlow turned on the Etch-A-Sketch and wrote:
Though this is a few years back, that's what I did. My original CPI unit
lasted about 70K miles. I then replaced it with another CPI, which lasted
about 20K miles and still under a GM warranty because of the issues) had
one at 120K miles - 40K miles later.
This last one was a newer MPI unit and lasted until I sold the truck at 158K
Does the fuel STAY working once the engine 'catches'?
I read somewhere there's failsafe code in the engine controller (from some
manufacturers) that has to see a manifold pressure drop during cranking
to keep the fuel pump on. (To prevent the fuel pump from just dumping
the entire tank on the ground if a line breaks) Anyway, if the engine
catches with starter spray, is the rail still pressurized but not getting to
I just remember hearing about the safety code when a friends car wouldn't
start. It would sputter once, then nothing. The problem was the MAP
sensor not seeing the vacuum from the intake. The sputter I suppose
was from the initial fuel pump running and pressurizing when you turn
the key on. The short buzz then it shuts off. But the pump wouldn't
restart when the engine was cranking because it didn't see the intake
pressure drop from the engine sucking air.
Stupid question??? Hey - there's no room for stupid questions in this
Yeah - it has gas. He had just put a half tank in the night before.
Once he put the new fuel filter in roadside, he had good delivery up to the
throttle body. (Wouldn't listen to dad and install that as part of the pump
installation...).Still no start. Looks to be a spider issue at this point.
This engine appears to be quite well known for this kind of failure after
installing a new pump at this kind of mileage (110,000 mi). I'd never seen
this before, but then again I'd never seen bare naked ladies mud wrestling
and sliding all over on each other either. Some things in life you just sit
and wait patiently for your first encounter with.
hey mike-I continue to think about this-my 2 cents worth, check out
the exact fuel pressure. I own many, many of these-I sell and service
em...In a world of percentages, my suspicion is towards the pump-that
causing a no start and the fact that I do very few injector
assemblies. Also, if an injector bit the dust-or two or three, it
should still start albeit not well. Just my thought-pressure gauge,
exact numbers, real tough to tell without it. There is my 2 cents
worth and today it's on sale for free! good luck!jp-hey mike you
could also(with the gauge) energize the system, take the reading at
the fuel filter(with proper adapters)to narrow it towards the tank-
that is if it indeed is! Keep us posted!
As it turns out, that is really the exact plan. Though it appears the
spiders are a common problem area, Sunday will be a fresh start. We'll put
gauges on the truck and see what is really happening. When you're on the
side of the road, you make some crude "measurements", and draw some hopeful
conclusions. This truck does require pretty high delivery pressure and I
know that it does not take a lot of pressure drop to fall below the minimum
level for adequate delivery. The thought that keeps nagging the back of my
mind right now is that even with poor delivery pressure, he should be
getting a start/run, albeit a poor run. Sunday will tell more of the
story... I'll post the final discovery after we're done.
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