zhock

Hi;
My 95 Blazer 4.3 just went dead while at 40MPH. I have fuel pressure on the rail, the dash lights and gauges all work but no spark. Can anyone tell me how to test the coil?

Also I have an OBD I engine but the system has an OBDII connection
I jumped the last two terminals on the top right and I get a 1+2 ‘Diagnostics mode’ I asked Auto Zone to test it and they told me a 95’ is OBD I and they are not able to test the OBDI. I am a little confused. Can I just get an OBD II scanner and check for codes??

I saw this on the FAQ by Blazee,
NOTE: Some 94 & 95 models do not have the B terminal. In which case a scanner is required.
NOTE: Some 94 & 95 models that DO have the A & B terminals still require a scanner.
All vehicles after 96 are OBDII, and require a scanner to access them.

Any suggestions would be appreciated.
Thanks, LS

old_master

Your system is OBD I, your code 12 is "system pass". Fuel pressure and ignition are not monitored by OBD so they cannot set a code.

The pink wire at the coil must show battery voltage with the ignition in the RUN position. The white/black wire at the coil should pulse ground when the starter is engaged.

Fuel pressure is critical on this engine. Key on, engine off, fuel pump running, pressure must be 60psi to 66psi and remain above 55psi for 3 to 5 minutes after the pump shuts off. Post your results.

zhock

Thank you, I will check the coil and pressures out tomorrow and post back.
Can you advise on the type of gauge they use? I will add it to the box.

zhock

Thank you, I will check the coil and pressures out tomorrow and post back.
Can you advise on the type of gauge they use? I will add it to the box.

MT-2500

Z or W code engine?
TBI injection or MPI ?
Z TBI engine are low pressure with no fuel pressure test ports/scrader valves.
On them best to get a fitting to tap in at fuel filter for a fuel pressure gauge hook up.
The W engine is high pressure and has a scrader valve fitting on left rear engine on in fuel line to test pressure.
A 100 lb gauge and a scrader valve fitting will be needed on it.

If old type dist plugs wire on top the dist has a ign module and a pickup coil in it.

First make sure the dist is turning and rotor is still on no one cylinder TDC compression.
And as Old master said 12 volt ign to coil.
And when checking for spark first test for spark out of coil and if spark there check for spark threw the dist and to each pspark plug.

Auto zone should be able to check/test coil and dist module for you.
Also they rent or loan or sell fuel pressure test gauges.
Or any good tool man or good parts place should have them.

If coil is good most no spark problems is in ign module and sometimes dist pickup coil or dist not turning like a striped dist gear.

On checking for codes on that one you will need a good high end /high dollar engine capable scanner for that year.

Let us know how it goes.
MT

__________________
Remember proper testing gives us the answer to many problems.
MT

zhock

Engine code is W and I do have the valve.
Couldn’t get a part number for the gauge so I went to the parts store, told them what I needed and hopped for the best.
The pump will push 62 psi and will drop to 55 in one minute.
There is system voltage at the pink coil wire, but there is no pulse from the white to ground.
Old type top terminal distributor. There was no spark from the coil when cranking.
I will strip the distributor and coil and run it over to Auto Zone for a check.

MT-2500

Ok let us know how it goes.

Make sure the dist shaft/rotor is turning before you pull dist.
MT

__________________
Remember proper testing gives us the answer to many problems.
MT

zhock

I had things checked out and the module was bad. It is now alive and kicking and I thank you both for helping me solve this. Spent most my life living with oil burners and I know that is no excuse.
I have one more question of concern. The Old Master stated that with the pump off the fuel pressure should maintain at least 55 psi for at least three minutes. It held 62 with power and dropped to 55 in 90 seconds with the key off. I did not see any indication of a leak on the regulator so I am guessing that it is just allowing more fuel that normal to return to the tank during operation. Do you think it is starting to fail or could it have been set up that way and may just keep on going. If you think it is a good idea to change it out based on those figures let me know and I will go ahead and replace it.
Again my thanks,
L S

MT-2500

You are welcome and thanks for posting back how it went.
You fuel pressure does not sound bad.
Feul pressure specs on a 95 code code w is 55/61.
Holding 55 after 90 seconds is not bad.
The main thing is to watch for a fast leak down.
Good Luck
MT

__________________
Remember proper testing gives us the answer to many problems.
MT

old_master

This site explains how the regulator works: http://www.picotech.com/auto/tutoria...actuators.html

It's a very simple design, and quite reliable. No need to replace yours, it's working fine.