Hello folks. I have recently bought a 1993 S10 Blazer w/ CPI and I'm having issues getting the thing running. I am fairly sure that the fuel pump needs to be replaced. However, I wanted to make this thread partly as a way to see if anyone could shed some new light on the situation, and also to try to get a lot of the information on this subject in one place: while doing research on this, there's a lot of good stuff out there, but a bit scattered. Hopefully I can try to help people who may have this problem in the future.

That said, I am still new to cars, so please please let me know if I have made a mistake with any of this, I'm trying to understand as well as I can and I want to make sure I have it right in my head.

Ok, so to start:
-When I first got it, I put the key in it, nothing happens.

-Checked the battery, this thing is about 6 years old. I tried charging it up for a few days and it took a charge but it cranked the engine really slowly and didn't hold a charge for very long. Replaced it with a new battery.

-Tried spraying starter fluid directly into the intake manifold, just above the throttle (I did this by just loosening the hose clamp holding the air intake on and moving that out of the way slightly). This didn't work, so I ended up taking the air intake completely off and holding the throttle open and spraying starter fluid well into the manifold. Cranked the engine, it burned the starting fluid! This tells me we have a spark (or fire as some of the older guys I know call it) and I assume there is some compression. If the engine isn't running, we must not be getting any fuel.

-Hard to say if the fuel gauge on the dash is accurate, but it's showing that there is about 1/3 a tank of gas. Added a few gallons of new gas, still nothing burning.

-Tried listening for fuel pump to turn on when turning the ignition key to the "on" position. (Should be able to hear the pump turn on for about two seconds, sounds like a faint buzz). Can't hear anything, assume fuel pump isn't working for some reason.

-Checked the fuel pump relay fuse. This is in the fuse box, under the dashboard, right next to the driver's door. Get access to it by removing one small panel held in by a screw. The relevant fuse should be "ECM B" which is listed in my owner's manual as protecting the "Engine Control Module, Fuel Pump" circuits. This is a 15 amp fuse. Mine is not blown, so I put it back in.

-Check fuel pump relay. This is where my knowledge starts getting a bit fuzzy. Apparently this is a device that takes a signal from a small circuit (like one that has an ignition key switch in it) and when that is completed, uses it to complete another circuit that may have more amperage in it (like a circuit going from the battery to energize the fuel pump). These relays are located, I believe, under the hood on the driver's side. They are mounted on the fire wall, mine had a bracket with two of them on it side by side. I took a couple pictures, not great quality but hopefully you get the idea. I took both of these out and tested them with 12V and a multimeter (there are various videos of how to do this on youtube, ericthecarguy has one I watched). Both of mine are fine.

So this is as far as I've gotten. I reckon the next step will be to test the signals on the lines going to the fuel pump relay to make sure it is getting turned on when the key is turned. If they ARE, I'm going to assume I probably need a new fuel pump, which probably means dropping the gas tank.

Thanks for any feedback, please let me know if I have overlooked or misunderstood something, or just how to make this more helpful. Like I said, my aim here was to both solve my problem and make it easier on people with the same issue in the future.

 

Welcome to the wonderful world of troubleshooting the fuel injection system on the 4.3L V6! Most of us on the Forum have been through this at least once, myself a few times as I've got five vehicles with a 4.3.

Find the fuel pressure and leakdown testing procedure here on the Forum. Kyle (swartlkk) has a link to it in his signature. It shouldn't be too difficult to find. Follow the testing procedures and figure out exactly what the problem is and where it is and you'll be able to isolate and solve the problem.

Good luck and let us know how it goes!

 

Thanks Toby. I think I have found the thread you referred me to: https://blazerforum.com/forum/tech-a...agnosis-23038/

I also just got a Haynes manual for the truck today so this should be a big help. I was able to narrow down the relay that goes to the fuel pump: it is the one on the right.

 

Update:

Since I know the fuel pump relay is working, I tested to make sure that the relay was receiving power correctly. I did this by disconnecting the plug from the relay and testing to see if a voltage went across the middle pin on the bottom row and the upper pin when the ignition switch was turned to "On". It was getting about 11.5 volts, which seems good to me.

Then I did a test to see if I have any fuel pressure at all. I went under the truck and loosened up the nut on the engine side of the fuel pump and cranked it to see if any fuel would spray out, which it didn't. Then I tightened that back up and loosened up the tank side nut on the filter, cranked it again. No gas sprayed out. I think its safe to say I need to get a new fuel pump.

As for which one to get, I see some conflicting opinions. Apparently ACDelco makes OEM replacement parts but I see one that's supposed to match this truck got some bad reviews on Advance's website. That pump is ACDelco EP381. I found a thread on here:

https://blazerforum.com/forum/2nd-ge...ommended-1021/

I'm having a hard time choosing between the ACDelco Ep381 and a Bosch kit seen here: Buy Bosch Electrical Fuel Pump Kit 69225 at Advance Auto Parts

Any advice?

 

go with the ac delco and check amazon.com could be 1/2 the price

 

 

Wow, that's a much better deal than anything else I looked at. I'm guessing the EP386 is just an updated EP381. I think I'm going to go with this and get the fuel filter at the same time and the strainer as well. Thanks for the advice and link! I wouldn't have thought of amazon for auto parts but I will have to keep it in mind from now on.

 

Sorry for such a long delay, not sure if this thread really needs any more updating but I will go ahead and add another post.
So I bought the EP386 fuel pump. Dropped the gas tank with help, and once we got it out it looked like all the rubber on the fuel pump assembly had been eaten up by ethanol so I went ahead and bought a new assembly. Brand name for that was Spectra Premium, it was on Advance Auto's website. This came with everything but the fuel pump, which was good because I had already bought that. Now I just need to clean the gas tank up a bit while I have it down, install the pump to the assembly, put the assembly back in the tank and see if it works.

 

darn ethanol!!! AcDelco pumps only!

 

Ok, to update:

This week i was cleaning up and painting the gas tank. Today, first thing was I replaced the fuel filter (made sure flow arrow was pointing in the right direction). I put the new fuel pump in the assembly and put the assembly back in the tank, put the tank back up under there where it belongs, and hooked up the fuel lines/filler hose/electricals. The engine still isn't getting fuel to it for some reason. It burns starter fluid fine, but as soon as that is gone it dies. I know the new pump is working, it is very easy to hear it running for a few seconds when the key is turned to on (before and after the key is turned to start) so I'm thinking the issue must be somewhere between the fuel filter and the engine. Either there is something mechanically wrong, such as something has gotten gunked or clogged up or possibly there is a computer issue where a signal isn't being sent correctly.

Any ideas of where I should check next? I have a basic idea of what I can do, but if someone can narrow down a specific area that is likely to be an issue, that would help a lot. Thanks guys.