I have a 94 series blazer with 4.3 CPI engine. I have replaced fuel pump, fuel filter, plugs, wires, module, both relays, cap/rotor and checked all fuses. It will run great for a few miles then just die. when its running I hear the fuel pump in the tank, then when it dies I cant hear the pump any longer. What could be causing this? I have spent over $400 and am out of ideas, PLEASE HELP!!

Try checking wires to fuel pump to make sure not losing ground and power. Also check to see if ingition switch may be going bad. These are just afew options. Good luck!

Are you sure the fuel pump is stopping? I ask because I have a 4.3 cpi engine in a '93 blazer and it cuts out also. I don't think the fuel pump is the issue for my car, it might be for you.
I have changed:
complete new cpi and supply line in the air plennum. New map sensor and spark module, new spark coil. Finally in desperation, I swapped out the entire distributer which includes the pickup coil. Fuel pump was changed last year. None of that has helped in any way other then I get better fuel milage than I thought possible now. It still cuts out whenever it feels like it.

The system is designed to shut down the fuel pump should the engine quit running. I've read of many folks that had problems with the key switch dropping power to the 'hot when in run' line but my digital dash stays up and even shows the rpm's as they fall off during a stall out. I've not managed to be able to hear if the fuel pump cuts out or not, but it should be off when stalled.

The frustrating part is I can't even determine for certain if this is a fuel problem or a spark problem--when it cuts out, it just dies and will almost always start right back up again.

Lately its been getting real bad to the point where it won't stay running more than a minute or so. I'm able to open the hood then and fiddle or move the wire loom where it goes into the spark coil and distributer and that seem to fix things long enough to get home.
Looking at the wire harness, I can find no bad connectors or any sort of water damage at all.
I'm ready to dump the blazer but just can't afford to do that this year. Hell, I can't even find reliable information to reset the timing after changing out the distributer--some posts on this forurm talk of an ecm wire to disconnect while setting the timing marks, others claim there is no adjustment. I have a Haynes manual that claims this information is in the engine compartment (not) and a 1000 page shop manual that refers me to another manual (that I don't have) to set timing.

I can tell you that the fuel pump relay is up behind the vacuum boost cylinder on the firewall--you can mearsure the voltage to the pump from there. You can also unplug the relay while the engine is running and see for yourself if that mimics the problem you are having. My theory is if the fuel pump cut out, the loss of fuel would cause the engine to 'die away' rather just cut right out as mine does. You should try that test and see if its the same for you.

So, does anyone else have any pearls of wisdom to drop in here? Like maybe how you solved your cut out problem?
John

When it quits check for lose of spark to all plugs.
You need ign spark to keep the pump running.
MT

An update on my '93 s-10;

I replaced the entire distributor--shaft, gear, module and all and still it quit running at random times.:banghead:

Almost always starts back up right away.:runaround: I installed a fuel pressure gauge so I could watch it during a stall--55psi all the time, a bit lower at idle --maybe due to lower alternator output at idle, but not sure. Its unrelated anyway.:popcorn:

In desperation, I swapped spark coils with a buddy who isn't driving his blazer at the moment. That seems to have fixed the problem. It idles smoother now and hasn't stalled since the swap. I have a new one coming from rock auto, should be here today.:iceslolan

I hope that cures the problem for my beast, but then you are never entirely sure with something that comes and goes like this. . .:headshake

Thanks for posting back the fix.
Glad all is well and going good.
If not done allreadt set the base ign. timing with aq timing light and you should be good to go.
Good Luck

I am not able to determine how to set timing on this engine! I can find no information from any of the manuals I've got. :headshake Do you have a procedure for it?
tks,
John

Disconnect the single tan wire/black stripe EST bypass connector and set base time to 0 degrees tdc.
Inside cab,
It is usually under heater housing where the carpet meets housing.
Pull carpet back and look for single tan/black wire.
Unplug the single connector.
Start engine and set timing.
The shut off engine and hook it back up.
May set code or check engine light if so clear code after setting timing.
Let us know how it goes.
Good luck