I have a 1995 Camaro Z28 with about 110,000 miles on the ODO and I need some help diagnosing a problem. I THINK the fuel pump is going bad but I'd like to have just more than a hunch before I start dropping the rear-axle and fuel tank in this weather.

The symptoms are as follows:

1. Cold-starting has been getting more and more difficult for the past few months. Now it takes a LONG time of cranking to get it to start (usually requires me jumping the car because the battery gets discharged in the process). When it's cranking it doesn't sound or feel like there's any combustion going on... it's just as if I was trying to start it w/o any fuel. Then it starts "all-of-the-sudden" and usually it will stall. It will restart quickly and sometimes stall again. Third start usually gets it into a lower-than-normal RPM idle. Then I can drive it.

2. If the engine has been started/run in the past half-day or so it will usually re-start without much of a fuss. That is, warm starts are not an issue.

3. Once it starts and in neutral, a slow throttle increase will result in a proportional RPM increase but if I hit the throttle hard the engine will hesitate and sometimes the RPM will actually drop. Occasionally if I hammer it I can hear a loud "bang" from the front driver's side of the vehicle... almost sounds like a backfire, but on the engine/intake side.

4. When I'm driving: during low loads the car drives OK, but will occasionally hesitate.... it gets me from point A to point B. If I step on it, it hesitates a lot and feels like it's either chocking or missing... and you can definitely tell that it has low power (feels like it's running on 4 or less cylinders.)

I changed the spark plugs, wires, and optispark at around 80k miles. I changed the fuel filter around that time also. I checked the catalytic converter to see if there was blockage but it's fine.

Any suggestions on what I should check next or how I can determine if the fuel pump is indeed the culprit without doing a remove-and-replace?

Thanks very much for your help,
Wayne

 

Try squirting fuel in the intake when you attempt to start it while it is having one of it's long start issues.

Get a fuel pressure gage like
http://www.sears.com/shc/s/p_10153_1...ting+Equipment
Tape it to the windshield and watch it during cranking, driving, accelerating etc.....

While I think you may have a stuck check ball in the fuel pump causing your long start issue, I don't believe it has anything to do with the hesitation. But the gage will prove that out.

Wouldn't be a bad idea to pull some plugs from both sides and see what they look like.

 

Those are some good ideas and sound easy enough.... I'll go pick up some starter fluid and AutoZone and see if they have a fuel pressure gauge that I can borrow. I just need to find out what the fuel pressures should be at idle, driving, etc. I have a service manual somewhere but I haven't been able to find it - yet (moved all my stuff recently)...

I found a couple of schrader (sp?) valves... one looks like it's for the A/C system, but there's another toward the back of the engine which looks like it's on the fuel rail. Guessing that's the one I need to plug the gauge into. Do you know, off-hand, where the fuel pressure regulator is located on the LT1?

I gotta find that service manual....

Thanks for the help speedygonzales... will update shortly.

 

The one you want is in back of the intake

 

43-46 with vac line disconnected (WOT)---about 8 less with hose connected.

 

Cool, thanks for the info! I got some starter fluid in a spray can... next chance I get (and there's someone around to assist), I'll try spraying some into the throttle body. I'm not sure how the MAF sensor will react not being in the intake path though.

I searched around an no-one is loaning out fuel pressure gauges. I'll have to call some friends, hopefully one of them will have one... hate to spend $50 on something that I'll probably only use once in my life.

Thanks again for the help.

ps: Z28 got a nail in the rear tire... but Discount Tire fixed it for free.... (not counting the 1.5 hour wait. LOL )

 

Friend came by with a gauge today... in idle the LT1 is getting about 28psi fuel pressure. When I drive and hammer it, it drops to around 15psi. I didn't know where the fuel pressure regulator was so I wasn't able to do the with-out vacuum tests... but either way, it's pretty clear that either the fuel filter is really clogged or the fuel pump is JACKED....

 

change out the filter. Then if the pressure is still low you can test the pump. One quick easy test is block the return with something like a vise-grip. If the pressure never comes up to spec you know the pump is bad. This can be done with out starting the engine. Just use the fuel pump prime connector.

Incidentally, check the vac line on the FPR to be sure it is not wet inside. If so, the regulator has a hole in the diaphragm.

 

Speedygonzales,
Yeah, I purchased a new filter today and I plan to change it out tomorrow. I found one of my service manuals but unfortunately it's not the one that talks about or shows diagrams of the fuel system.

Would it be easy for you to describe for me where the Fuel Pressure Regulator is?

And if it's not too much to ask, which is the return line to the pump?

I'm still digging through my boxes and I hope to find the other half of the manual... pictures are worth a thousand words they say!

Thanks again,
Wayne

 

I changed the fuel filter today... no improvement.

Looking at the engine it looks like the fuel pressure regulator is near the back of the engine head. There's a short line attaching to it which looks like a small vacuum hose. I pulled the hose up and off and it looks dry but I guess I should stick something inside like a q-tip to check since the opening was only 1/4" or so.

With regard to the fuel lines, there are three lines that go into the engine compartment... one goes to where I attached the fuel pressure gauge and then into the side of the head. The other looks like it goes through a little filter (should I replace that also?) and then into the back of the head. I didn't have a chance to follow where the third line went...

.... but I did just find the other half of my service manual so hopefully there will be some nice drawings/schematics in there.

Thanks again for the advice and help!
-Wayne

 

The three lines going back to the tank are fuel inlet to the rails, fuel return line and a vacuum line that eventually ends up at the charcoal canister behind the left rear fender liner.

The inlet and return lines are easy to identify. The fuel inlet to the rails is connected to the rails and is slightly larger than the return line. The smaller return line is connected to the fuel pressure regulator. Shown here courtesy of Shoe (Rob)

 

Ooooo la la! That's a great photo! Here I thought the regulator was the round black piece that's mounted sideways and I thought that the fuel pressure regulator was the "filter" that I mentioned! LOL! How embarrassing....

My buddy is bringing the fuel pressure gauge back today so I can check the FPR with the test you suggested (clamping off the return line). I'm 95% sure it's the fuel pump but the FPR is worth checking since it's an easy test and removing the fuel tank is going to be such a PITA.

Thanks AGAIN for the help. BTW, where can I find more such nice photos? I finally found the service manual but the drawings in there aren't the greatest and sometimes it's like looking for a needle in a haystack. These are much more clear and helpful in identifying the parts.

Peace,
Wayno

 

shbox.com has tons of info and pics

 

Thanks for the help guys... got the FP gauge back and even with the pump running and the return line clamped off it does not make more than 30psi. The vacuum line to the regulator is dry and it's providing good vacuum at idle but pulling it off makes no difference when the car is running because the pressure is so low to begin with. I didn't realize that the rubber portion of the fuel lines were just covers for the nylon tubing... I hope I didn't crack them. So far no leaks or flames so that's a good sign.

The shbox images came in handy again because I couldn't find the FP prime connector... it was buried under the plastic conduit and I don't think I would have been able to find it otherwise. BTW, where the heck is the FP relay located? It's not in the fuse/relay box under the hood.

Now for the hard part... replacing that fuel pump. Anyone know of a good "How-To"? I usually find those more user friendly then trying to follow the service manual.

A friend of mine didn't bother dropping the tank, he had some guy cut through the trunk and replace the pump that way... any thoughts on if this is acceptable or should I do it the long and hard way?

Again, thanks and Happy Holidays.

 

The fuel pump relay is under the driver side dead pedal. The left kick panel needs to be removed to get to it. But since your pump runs, you need not pull it.

Do the panel trick from the trunk area. Just be sure to prep the piece you cut out so it seals well and does not rattle when you put it back. Simply do a search in this forum to find several instructions on how to do it. Although, you really only need the "where to cut the hole" portion of the instructions. The rest is self explanitory. I think you will need the spring release tools to get the fittings off. Like the ones on the fuel lines up front. shown here:
http://www.lislecorp.com/tool_detail.cfm?detail=604

It's been so long since I was at the tank I may be mistaken.

Be extra cautious with the float sending unit when you put it back in. I recommend trying it before you button it up. Many peeps have wrecked the fuel gage when they put it back in. Simply plug the unit in, place it in the tank and turn KOEO and see that the level goes up on the gage. Be sure you don't have more than 1/2 tank of fuel when doing the job. It's cleaner that way.