My 95 Blazer is hesitating at random times details below), and since the fuel filter is basically the cheapest thing to replace, I want to see if that will fix the problem. Where is the fuel filter located? I’m guessing on one of the frame rails but I haven’t checked yet. Do I need to depressurize the fuel system before disconnecting the lines? If so, how? Are any tools needed to remove the hoses from the filter? Would it be better to replace it after the truck has been sitting overnight, or would it not make a difference if I replaced it right after driving? Could a clogged fuel filter cause the truck to not start? (it has done this twice already). Any recommendations for the easiest way to change the filter?

The hesitation problem: it’s most noticeable at the top of first gear (like 3000 rpms and 25-30mph). When going steady at 50mph the rpm drops very slightly like every 5 seconds. It’s not noticeable at idle. I let the truck warm up at least until the temp gauge moves (it’s been around 40º here), and when I rev it, sometimes it will hesitate. Sometimes it will be completely fine after 15-20 minutes of driving. A few days ago it wouldn’t start, so I charged the battery and after a lot of cranking it started. Then I let it warm up and drove a few miles and shut it off. Then it wouldn’t start and the battery died again. So I charge it and put it back in and it fired right up. I am really confused as to what the problem could be if it isn’t the fuel filter. I hear the pump turn on every time I turn the key.

 

To properly diagnose a fuel system problem, you really need to have a fuel pressure tester. You should look at the pressure with the key-on, engine-off and it should be between 56-60psi. It should remain at 55-58psi with the engine running. Then after you turn it off, there are checks for loss of pressure (aka leak between the pump & the injectors). It is not uncommon for the CPI unit, specifically the fuel pressure regulator (FPR), to leak and could cause the problems you are experiencing.

I suggest you either rent/borrow a fuel pressure tester or buy one and test the pressure. If you do a search on here for 'fuel AND pressure' (copy and paste without the single quotes), you should find another post by me that has the complete details for testing the fuel system. Those details are for the newer CSFI vortec engines, but they should still apply.

Also, the fuel pressure should snap up when you first turn the key on. If it takes awhile to build pressure and you don't loose pressure, then you have a restriction in the line. A restriction could either be a kinked line or a clogged/plugged fuel filter.

 

A partially plugged fuel filter could be your problem, or it could be a dieing battery. Have the battery tested while your buying a new fuel filter at your favorite autoparts store. Even if it is your battery, you can never go wrong replacing the fuel filter.

To relieve the fuel pressure, take off the gas cap, and push in the schrader valve until gas stops coming out. I recommend a rag to catch the fuel. No special tools are needed to remove the filter, unless it has screw on fittings. Then I highly recommend flare wrenches. Sears sells a whole set fairly inexpensive, get the standard sizes, not metric. You don't want to round off the nuts on the fittings, and regular wrenches tend to round off those nuts. If you do round them off, no biggy, however you turned a simple project into a bigger project that requires more special tools. Like a double flaring tool, small pipe cutter (or hacksaw, file, and compressed air), new fuel line, and a new fitting.

 

You can also relieve the fuel pressure by pulling the fuel pump relay and cranking over the engine. It may fire, but it won't run for long. This is a cleaner way of doing it.

I second the flare wrench set. I used liquid wrech (or equivalent) on my fittings once a day for 3-4 days before I attempted to replace my fuel filter. Didn't have the proper flare wrenches but the liquid wrench loosened up the corroded flare nuts so it didn't come out difficult at all.

 

I change my fuel filter on my '95 Blazer yearly.. as a routine maintenance item. Yes - it's on the frame rail. 2 wrenches needed.. one to turn the nut, one to hold the other nut.

I *HIGHLY* suggest wearing either safety goggles or a face shield when removing the filter. It can drip or splash into your eyes when it's initially disconnected. (DAMHINT = Don't ask me how I know this) Get some old rags/newpapers to soak up the little bit of gas that will leak from the open line...

While you have the filter off, check the condition of the o-rings on the flared ends of the fuel line (if your Blazer has them). If they're worn, cracked, or missing, please consider replacing them (with a similar fuel-resistant o-ring). Easy to do.... takes me all of 10 minutes to do, and that includes *finding* my correct open-box wrenches in my messy workshop.

As for de-pressurizing the lines... Although I read it in the Haynes manual, I've never de-pressurized mine to change it out... in fact, I'd never seen the schrader valve until I replaced the fuel pressure regulator/injector spider/nut kit last year.

My only mishap (in the mentioned DAMHINT in the above paragraph) was the first time I had changed the fuel filter - probably 8 years ago - and happened because I was stupid, and (a) didn't think about where I was laying under the Blazer when I disconnected the filter, and (b) was stupid and did not wear eye protection. Please protect the peepers. If there's a chance of a drip or splash of a chemical that will do harm to body-tuissue.. then protect yourself.

G'Luck with the other symptoms you describe. Sorry - I don't have any suggestions for those...

Rex S.

 

Do they sell fuel pressure testers at Autozone or similar places? One time when it didn't want to start, I kept cranking it and it eventualy built up enough pressure to start, however one time after cranking a lot it didn't start, but it fired right up 2 hours later.

It's not the battery, it only died because of how many times I was cranking it to see if it would build pressure

I bought a creeper and took a look at the filter. Here is a pic
Those look like regular nuts, so would I just be able to use 2 different open ended wrenches, or would I need flare wrenches? I gotta find my can of PB Blaster.

Funny that you mention pulling the fuel pump relay, as I got the truck cheap because the previous owner thought it needed a new fuel pump. So I towed it to a shop and I tried switching the relays and it fired right up. Saved me the hassle of replacing the pump.

I think the purpose of de-pressurizing the system is so that it won't splash in your eyes when you disconnect it, but I will find my old chemistry goggles just in case.

Oh, and the truck has like 227k miles on it.

swartlkk - I tried searching for your post, but it returned tons of results. Do you have a link to it? Are you a member on clubgp.com? Theres quite a few SSEI owners there. I have a 1998 GTP Pace Car

 

I have poked my head into the CGP boards from time to time, but its more of a hassle than a help due to the juvinal nature of like 75% of the members. I am a member of the UNYCGP (Upstate NY CGP), but even some of those guys are a bit under developed in the knoggin' and resort to name calling first and foremost. I can't stand crap like that.

Anyway, if your fuel system is working properly, you could have 55psi or more in the line. Crack the flare nut loose and PSSHHT. It'll only spray out for a bit, but your head will be right under it! By depressurizing it, you won't have this problem. It'll only drip what is just sitting in the lines. I find pulling the relay and starting the vehicle is the easiest way to depressurize the lines. And that way you know that if someone were to turn on the key while your down there, you won't get a rather large face full of fuel!