Running out of ideas...

I have a 2000 ZR2 Blazer

I first replaced the fuel pump and filter with new ones after the fuel pump died.

Than it started running rough, and then died soon after.

We've replaced and checked ignition system parts as follows; cam shaft sensor (used), rotor & cap, wires & plugs, ignition coil(new) & pack(used). Changed the oil too. Also tried swapping the "computer" out with a used one, but after we got it started we went back to the original one and still started.

We got it started and it ran for a day. Rough starting when applying gas from a stopped position...but it ran good while driving at road speed. The second day I started it and drove it for about 10 seconds when it started to spurt, I gave it more gas with no change in power, and than it died after sputtering out for 10 more seconds.

When we try to start it now sounds like it spurting for a few seconds and when we stop cranking the engine sounds like it back fires (like it's "dieseling").
Looking inside the throttle body reveals a dark splash that smells like gas as if the engine through it up. I understand that we'll have to change the oil again due to unburned gas eventually.

We've given the mass air flow sensor a good cleaning with alcohol, changed the air filter.

Cleaned the Battery Terminals.

We've also tried spraying the Quick Start stuff in the throttle body with NO Starting just sputtering.

I think that's it so far if I've missed something I'll post as I remember and if do anything else.

Running out of ideas, this sucks because my classes start in a few days and would like to be able to drive to school.

Any help would be appreciated.

JP 613-869-7511

 

It wouldn't be the first time a new fuel pump proved faulty.
96+ Fuel System Diagnosis

 

We checked for a spark on the plugs. Good Spark.

We tried pouring Gas into the throttle body while cranking with NO start at all.

Should it not at least start for a few seconds?

 

As asked already, have you tested the fuel pressure and the leak down rate? The pressure should rise to >55psi and it should hold pressure without dropping more than 1-2psi for at least 10 minutes after the pump shuts off.

Fuel into the throttle body won't help if you a) already have too much fuel in there, b) don't have adequate spark, and/or c) you don't have properly timed spark.

 

Checked the fuel line pressure today and it held at 60psi for a long time with minimal drop.

A friend suggested that it may be the the spider in side the intake manifold, he told me that the little tubes on them could crack and brake.

 

Going forward with my trouble shooting, we have tried starting the engine multiple times with no start...

Checking the oil reveals a gasoline odour and therefore we have changed the oil several times over the coarse of our repair adventure.

We have also noticed after the last time we changed the oil that the level on the dip stick has gone up considerably which is another reason it may be the "spider"

Any suggestions would help.

 

If the oil level is rising drastically due to fuel contamination, the fuel pressure should not hold steady after the pump shuts off...

The SCFI engine uses a central injector pack where the electronic injectors are housed. Each individual injector then has a line down to a pressure actuated poppet nozzle which resides in the intake manifold positioned directly ahead of the intake valve port in the cylinder head. The injectors shouldn't leak that much by if they were leaking along with the line to the poppet nozzle leaking and the injectors would need to be opening for there to be a leak.

The typical location for a leak would be at the FPR (fuel pressure regulator) located at the back of the main injector housing/body, but again, a leak would show up on a leak down test as a rapid drop in fuel pressure.

 

Hey JP, saw ya called, sorry was visiting pops in the hospital (don't ask)... Anyhoo, without seeing this thing, it's kinda tough. In regards to the previous reply (and I'm not into forum bashing, just being honest) I've done at least a half dozen spiders on trucks with your same or similar symptoms. The truck will pass the leak down test because the central injector won't open to push fuel through the spider to the poppet valves at the injectors until you crank it. No leak down proves the fuel pressure regulator and the check valve in the fuel pump are both holding pressure; it won't diagnose a bad spider; about the only way I've ever confirmed that is lifting the top of the manifold off. What I've seen happen is the spider springs a leak and floods in the intake, causing either a fuel trim lean code (small leak and still running) or a no-start and flooding (like yours perhaps) Also, could even be a coolant temp sensor gone weird, showing a coolant temp of -40, which dumps way too much fuel, causing flooding (seen this a lot in 4.3's and 5.0's) Try unplugging the CTS and starting it, might go into limp mode and start if that's the problem. Wish I was closer; a quick scan of the data stream tells a lot.

 

A leak at the body would show up on a leak down test given the configuration found in the subject vehicle.

The 96+ SCFI spider is not like the older CPI engine where there is only one injector that then feeds down into a distribution block (inside the main spider body) and out to the 6 fuel lines to the poppet nozzles). There are 6 individual injectors on the 96+ SCFI engines, one for each cylinder. The injector is sealed to the spider housing as well as sealed to each individual fuel line running down to the poppet nozzle. There are no pressurized passages shared with the injector body between the injector itself and the line running down to the poppet nozzle so a leak in the body itself would show up on a leak down test.

For a leak in the line(s) to cause a noticeable rise in oil level, the engine would either need to be cranked over for a very long time, or the injectors would have to be maxed out all of the time. The CTS sensor is a good thought.

 

my 92 S10 Blazer will not start with the coolant temp sensor disconnected, I tried that Saturday, when I plugged the coolant temp sensor back up, it started instantly.


From my experience on my 92 S10 Blazer the fuel pump runs for about 4 to 8 seconds after turning the ignition switch on without starting the engine, and it will not come on again until I either start my engine and or turn the ignition switch off and turn it back to the on position.

So if there is any leak past the fuel pump it will not hold 60 pound of fuel pressure.