95 Blazer, No Spark, No Fuel

Just purchased 95 LT Blazer 104K. Person that had it thought it might need a fuel pump because it wouldn't start. When I went to pick it up I was told that someone else thought it might be electrical and not the fuel pump. I was told that someone had replaced the engine computer with one from a 96, the 95 computer was on the front passenger seat and the blazer did not have a battery. I put it on my car trailer and towed her home.

Brought it in the garage, checked fuses, all checked ok. Checked for spark and had none, checked for fuel and had no pressure. I removed the 96 computer and put the 95 back in (16193495) now I am pretty sure you can't use the 96 computer in the 95. Still Having no fuel pressure and no spark I think that the computer might be bad still. Anyone else have any helpfull suggestions?

Did you check the coil?

Did you check the CPI fuel injector?

Checked the coil, obviously no spark. Apparently that is the second coil from what I was told by the prevoius owner cause they tried that too. I did not check the Fuel injector due to the fact that the pump isn't even priming at all. No power to the pump.

The best thing at this point is to take one item and check it out such as fuel or spark. You checked the fuses, did you check if they all had power to them? With the parking lights on and the key in the run position, all fuses should have power except the crank fuse. By the way, you are right about the computers, the fuel delivery systems are different.

To make sure that we're on the same page, on your option label, which engine do you have L35 or LB4?

Just purchased 95 LT Blazer 104K. Person that had it thought it might need a fuel pump because it wouldn't start. When I went to pick it up I was told that someone else thought it might be electrical and not the fuel pump. I was told that someone had replaced the engine computer with one from a 96, the 95 computer was on the front passenger seat and the blazer did not have a battery. I put it on my car trailer and towed her home.

Brought it in the garage, checked fuses, all checked ok. Checked for spark and had none, checked for fuel and had no pressure. I removed the 96 computer and put the 95 back in (16193495) now I am pretty sure you can't use the 96 computer in the 95. Still Having no fuel pressure and no spark I think that the computer might be bad still. Anyone else have any helpfull suggestions?

Well, you can use the 96 computer, but it has to be reflashed for the 95... That said... To test the fuel pump directly, apply direct 12 volt power to the loose wire against the firewall on the drivers side. Do this with a pressure gauge hooked to the shrader valve. The fuel pump should turn on... Now, at this point does the motor crank when you turn the key? Do you get interior lights et-al?

Now, Check the crank position sensor on the bottom of the timing chain cover. Check all connections to the distributor. Check your cap and rotor... Then if all that is ok, start tracing the engine harness.

To test the fuel pump directly, apply direct 12 volt power to the loose wire against the firewall on the drivers side.

Ok I did this and all I got was a spark like the wire is shorted out somewhere. I can hear the fuel pump click when the wire sparks. So I think I am gonna disconnect the wires at the fuel pump and apply 12 volts to the jumper wire again. If I get another spark then it will be a short in the wire somewhere. If I don't My guess is the fuel pump.

The only thing that is weird about the whole situation is the vehicle is not getting any spark. ALso my obd II read and erase scanner will not connect or link with the computer. I have a new computer on the way hopefully it will be here today. I had to give them the vin# and the mileage so it could be re-flashed. I'll post later with any progress.

It's interesting that you said that the fuses were all good. IF the bypass wire is sparking the way it is indicating a short, you'd think you'd have had a blown fuse (unless it's a short prior to the wire tying into the fuel pump circuit).
My wife's 95 Blazer was being tempermental a couple of weeks ago and would not start. I thought it was a probelm with the ignition interupt on the alarm system but after much head scratching and a couple of days, I traced it to a loose relay in the glove compartment. The center relay of the three in the glove compartment is for the fuel system. Might be worth checking.
I have to say, the direct wire to check the fuel pump is one of the few good engineering ideas I've seen on this SUV.

Al T.

ALso my obd II read and erase scanner will not connect or link with the computer. I have a new computer on the way hopefully it will be here today. I had to give them the vin# and the mileage so it could be re-flashed. I'll post later with any progress.

If you cannot link to the computer, then the computer is either fried or not getting any power.

No Computer = Your ODBII code scanner won't work.
No Computer = No Spark - It controls the spark.
No Computer = No Fuel Pump - It controls the fuel pump.

No Computer = Don't expect very much to work.

I would focus on that problem. Start with the fuses. You could try putting in the other computer, and see if your ODBII scanner can scan that one. Tis always better to fry your test computer, rather than the new one that you have on order <GRIN>.

Once you have a 'living' computer, then work on Fuel / Spark if they just don't magically re-appear once the computer comes back to life.

Kindest Regards,
----- Robb -----

Ok ALso my obd II read and erase scanner will not connect or link with the computer.

This car is not truely OBD II That may also be why it will not link up with the computer.

This car is not truely OBD II That may also be why it will not link up with the computer.

Your quite correct, but it really does depend on exactly what kind of computer is installed in the 95 (there are two types).

Many 95 owners in this forum, with VMC-A are able to use a standard ODBII scan tool on the 1995. I've also read the the VCM-A can be upgraded so it's fully ODB compliant.


I removed the 96 computer and put the 95 back in (16193495) now I am pretty sure you can't use the 96 computer in the 95

Sounds like he has VCM-A (Must be located on right Hand Wheel Well under the hood to be VCM-A if not, then it's not VCM-A), otherwise the VCM from the 1996 I suspect wouldn't even plug in properly.

Given that it appears he has VCM-A, then I don't see why it wouldn't scan using an ODBII scan tool.

Regards,
---- Robb ----

Ok, did the following today:

Disconnected the fuel pump and tried applying 12 volts to the jumper wire of the fuel pump, and it did not spark. So I replaced the fuel pump, and applied 12 volts again, now the pump comes on. Still no spark on the ign end. I got the new computer and installed it. Still no spark. Then replaced the coil, guess what NO spark! I have yet to check the distribitor which I should have allready done. It is just so hard to get at. The funny thing again is that the pump does not prime for the 3-4 seconds that it is supposed to when you turn the key on either......

When you installed the new VCM, did you transfer the Spark Control Module? Was it already programmed to your Blazer?

When you installed the new VCM, did you transfer the Spark Control Module? Was it already programmed to your Blazer?

Yes I replaced the Spark Control Module and it was re-flashed to my Blazer. I am going to probally check the crank sensor today. If the sensor is bad: NO spark....That still dosen't solve the fuel related issue though.

First check the pressure at the shrader valve on back of the intake (should be 56-60 when trying to start) Have you checked the ignition module bolted to the coil? I reccomend grabbing one from a junk yard... That said, if you're still not getting spark it may be distributor related. Has anyone pulled that distributor before? It may be 1 tooth off in either direction which will not allow it to start. Next check for spark at the coil itself. Pull the wire from the cap side and put it to the block when trying to start. If you get spark from the coil, but not at the plug wires then the fault lies in the distributor module or cap/rotor...

First check the pressure at the shrader valve on back of the intake (should be 56-60 when trying to start) Have you checked the ignition module bolted to the coil? I reccomend grabbing one from a junk yard... That said, if you're still not getting spark it may be distributor related. Has anyone pulled that distributor before? It may be 1 tooth off in either direction which will not allow it to start. Next check for spark at the coil itself. Pull the wire from the cap side and put it to the block when trying to start. If you get spark from the coil, but not at the plug wires then the fault lies in the distributor module or cap/rotor...

1st. there is no shrader vavle. The only way to check fuel pressure is to take out the fuel filter and check from there. Second why check pressure when the pump is'nt even priming? I have checked the ign module and the coil, both check out ok. I pulled the distributor cap off and everything looks to be ok. I replaced the crank sensor this morning and still no spark. On the car trailer it went to my buddy's shop. I'll let eveyone know the progress.

There is no shrader valve???? Then something is seriously wrong with that setup as every engine since at least 91 has a shrader valve on the fuel lines where they come into the plenum. It's integral to the nut kit. The reason I said to check it is incase you may or may not being hearing it. Like I said, doesn't hurt to check it.

There is no shrader valve???? Then something is seriously wrong with that setup as every engine since at least 91 has a shrader valve on the fuel lines where they come into the plenum. It's integral to the nut kit. The reason I said to check it is incase you may or may not being hearing it. Like I said, doesn't hurt to check it.

There is something seriously wrong with the truck, but not because there is no shrader valve. Not every vehicle since 91 has a shrader valve. If you look into the chilton's or Helms manual it even tells you to take out the fuel filter and use a T connection to your fuel pressure tester. No it dosen't hurt to check the pressure but it is loud enough that you can hear it so why even waste my time?

There is something seriously wrong with the truck, but not because there is no shrader valve. Not every vehicle since 91 has a shrader valve. If you look into the chilton's or Helms manual it even tells you to take out the fuel filter and use a T connection to your fuel pressure tester. No it dosen't hurt to check the pressure but it is loud enough that you can hear it so why even waste my time?

95s have shrader valves so lets drop the arguement of it having one.

95s have shrader valves so lets drop the arguement of it having one.

I don't remember there being an arguement, looks more like a discussion to me. Now if you're telling me that 95's have shrader vavles then why dosen't mine?

It does.. Look at this picture. You will see that little black cap on the top line on the outside of the lower intake... That is the shrader valve..Just follow your fuel lines.

http://www.pghconsulting.net/teal/nutkit1.jpg

Yip, and there it is.

It is on my 1995 too.

Bryan

What did you finally replace / fix to finally get it running? I have the exact problem with a 1995 blazer.

Bryan

What did you finally replace / fix to finally get it running? I have the exact problem with a 1995 blazer.
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