CPI injection trouble shooting - power + gass = no spray

Hopefully this thread can be answered by someone, because I am lost now on what I can do.

92-95 CPI 4.3L "W" engine out of a s10 blazer. Only info I have.

The fuel pump went on my truck, I was able to replace it and redo the wiring harness. All is working, how ever my truck will still not fire. Everything up until this point was working fine. Already tested for compression and spark.

We pulled off the plenum and tested the fuel injector. Power was there but nothing came out the injectors. I went to the wrecks and picked up 2 spider units.

I have since then tried both of them, and neither of them have fuel coming out the injectors during crank. I have done the 194 bulb test on the injector harness, and I see it pulse. I have 12Vdc coming out of them on my dmm, and it dips a bit during crank.

I changed fuses on my ECM and ignition just in case, but none of them were blown.

Fuel pressure is around 13PSI during crank. Which is standard out of the mechanics book I have for that engine.

I really don't have 300$ to drop on a rebuilt spider but if I have too I have no choice. I just find it hard to believe that 2 spiders I pulled out both don't work, but at this point its all I can think of.

Thanks

The specs in your manual for the CMFI (W) engine are incorrect, (must be a Haynes or Chilton) time for a new manual ;)

1992 through 1995 CMFI systems use two different specs so you need to know which year engine you have. 1992 through 1994 requires 55psi to 61psi. 1995 requires 58psi to 64psi. These specs are with the ignition ON, engine OFF and fuel pump running.

On 1992 through 1994 pressure must remain above 50psi for 3 to 5 minutes after the pump shuts off. On 1995 it must remain above 53psi for 3 to 5 minutes.

The poppet valves require around 40psi to open and squirt fuel. At 13psi there isn't enough pressure to open them, that's why they aren't squirting fuel. Check fuel pump maximum output at the fuel filter, should be around 80psi to 100psi. What brand fuel pump did you install?

It sounds like they might have given you a fuel pump for a TBI engine and not for a CPI. Post the part number on your receipt to confirm.

I picked up a new fuel pump today. I got 60PSI at key on. Put everything back together, and it still did not fire.

Even tried a shot of ether down the intake, still nothing. I have spark, and fuel coming out the injectors now. So I am lost as to what else it might be. Going to grab a bite to eat and test the timing of the number 1 cylinder tonight.


How hard is it to change on this engine? Anyone have any how to's for this one, and any tips on checking the timing.

Thanks

Do you have a blue, (not orange) spark at each spark plug while cranking?

Check/adjust ignition timing, (while cranking) with the EST wire dosconnected. The EST connector is behind the carpet, passenger side, near the top edge of the carpet under the dash.

I was told to check my timing gear, so I am about to start the process of that. I also cranked the engine for a couple seconds and noticed my sparkplug is soaked.

I tested 3 random spark plugs and they had a blue spark. But on s10planet someone suggested that once their inside my engine their might be to much resistance and my cap/rotor/wires might need to be replaced. Since he had a similar problem.

I took them off a few days ago and they were bad (but worked fine before when truck was running) and I cleaned them up with some sandpaper. Maybe I did something wrong?

I am going to do a few problem solving steps I have been told, so I will update the thread in a few hours

Stick a timing light on it, that will tell you very quickly if it's in time.

Timing and compression test are done.

Compression was around 120PSI.

I used the how-to thread based HERE (http://www.automotiveforums.com/vbulletin/showthread.php?t=881442). It happen to have the same engine block (missed what truck he was working on) so I assume he had a similar engine to mine. Since the 1 and 4 positions where the exact same, and same markings on the balancer.

Just before TDC the rotor seemed to be either just before or on the #1 cylinder plug. At TDC it was on or just a bit after the spot I marked. I was doing this myself so I struggled a bit crawling undernearth turning a little bit at a time then checking then repeat.

Now I had a compression gauge in the spark plug hole and I was getting nothing th entire time, even as the cylinder was suppose to be building up compression, but I guess turning the engine manually causes the air to escape faster then I can see it. I didn't clue into that until later. I was unable to get my thumb over the whole and turn at the same time, but the rotor seemed to be timing the stroke perfectly, so I assume its on the compression stroke and that the timing isn't off to make me think otherwise.

So now my question is, what the ****? lol I am lost what to do now.

I have had issues with scanners not reading my truck so I doubt the plug in my truck is wired correctly. Do anyone of you know have a how to on wiring one up to the computer so I can check the wiring and also how to reset my computer?

Thanks for all the feedback.

Also, gave a tune up with new cap rotor plugs and wires. Still no attempt to fire. Spark is clear and strong