I have a 1986 Iroc-z 305 that had been parked for about six months.
Four days ago, I went to move it, and after turning over a few time it fired up, and after driving around all afternoon, turning it off and on several times I parked it for the night, the next morning I went to start it and and nothing, it will turn over but never run.
I tried starter fluid and it will start and idle for a second but if I give it any gas it dies, so I was thinking maybe a fuel problem, but I can smell raw gas coming out the tail pipe.
The one thing I have noticed, is that if I disconnect the MAF (mass airflow sensor) it will start and idle rough and of course if I give it any gas it dies.
So am I on the right track with the MAF? Or is there something else I'm missing.

 

I just had the same problem with my GTA. Turned out to be a MAF sensor. Autozone has the best price, $125 for a reman. I would almost guarantee thats your problem because mine just went out over night the exact same way. The car ran great the day before and one morning it just wouldn't run for anything.

 

one of the flaws of the MAF system...

 

Tried putting a new MAF in but it made no difference.
Going to start checking sub systems.
Finally got the car to a place I can work on it, only took 9 months!

 

change the fuel filter its cheap and may fix it gas does go bad and if it sat 6 months could have broke up old nasty crud in tank and plugged filter hence idle only not enough fuel getting through to rev

 

Alright, better bring everybody up to date.
In the last few weeks I have replaced the fuel filter, fuel pressure regulator, ignition control module and a some sketchy wire connections. the wire plug's for the TPS and IAC are in really bad shape, I ordered new plug's and should get them in a few days.

So as of right now, here is what happens when I try to start it.
When I turn the key it will sputter for a second or so like it want's to start, if I try again nothing, it just turns over. If I let it sit for maybe 5-10 min it will sputter again, then nothing.
If I use starter fluid, it will start up for a few seconds then die, however, if I unplug the TPS and MAF sensors I can get it to start and idle (poorly of course) and if I am gentle I can rev it up to about 2000 rpms but no further.

I was also just reading on this forum that these cars need really strong spark, so I will be looking into that also.

 

try cleaning the throttle position sensor with some carb cleaner it might be sticking

 

That's what I was thinking but it's a sealed unit so there is no way to clean it, the peg moves smoothly though.
I ordered a new TPS sense it's not too expensive.

 

Never clean any electronic component with carb cleaner. Dont even spray the wiring with it. Carb cleaner is made for carburetors, not for sensitive electronics. It eats plastic. Like the OP says, the TPS is sealed and cant be cleaned anyway.

The TPS is almost certainly not your problem. Unfortunately, you have an 86 TPI. These had a one year only MAF controller. You replaced the sensor but I doubt you replaced the controller. These babies run about $350 at the cheapest and are not available except for cheap aftermarket repros(A1Cardone). If the controller fails, the MAF doesn't work. And the controller fails alot. You really need to get your hands on a good service manual, or atleast search down the test procedures for the MAF system on your car and complete the tests before you buy anymore parts.

 

I need to edit some of what I said about your MAF sensor. It was the 85 that had the unique MAF module, not the 86. The remainder of what I said still stands.

 

Silly question, but have you checked to make sure you did not fail a fuel pump? Sometimes after sitting, they will develop varnish-like coating on them and stick later (shortly after). The simpliest way is to key up and see if you hear the 10 sec prime. if not, you'll have no pressure. Also, verify you have spark.

 

The fuel pump usually prim for about 3 sec, every so often it will run for close to 10 sec.
I haven't checked the fuel pressure in the fuel rail, none of the auto part stores in town have a gauge kit that fits my car. There is pressure in the rail, I have got fuel to squirt out of the nipple adapter. (No boob joke intended!)

I am going to check both the MAF power relay and the MAF burn off relay, looks like one or both could be the route of my problem.

 

I checked the MAF power relay and the MAF burn off relay. Both look ok, the connection plugs look like they cold use some cleaning though.
I ordered new relays sense they are cheap.
If I disconnect the relays and start the car it does the same thing as if I disconnect the MAF sensor, not sure if that means anything or not.
If the new relays don't fix the problem, I will start going through the wiring. Yay!

 

Before you write off the fuel, spray some starting fluid in the air tube and see if it starts to beat

 

You should really have a scan tool for this issue. Viewing ECM data would reveal a MAF sensor issue right away. The best alternative to a scanner is a DVOM tapped into the MAF signal circuit at the back side of the connector. MAF signal voltage should range from about .5 to 1v at idle to about 4.5v at max air flow.

 

Are you talking about ECM Codes? or something that is reading data real time?
I can read the ECM codes, when everything is plugged in I can't get it to run long enough for any codes to show up. When I run it with the MAF unplugged, I get code 33, which is for the MAF.

 

So I finally got a fuel pressure tester, I hooked it up to the fuel rail and you know how much Psi there was?
6 Psi!!! So looks like I am dropping the tank Yay!

 

Did you already verify that your FP is solid?

 

what is the best way to check the fuel pump? apart from taking it out of the tank.

Do the fuel pumps die slowly? Or do they tend to just quit.
It might be that there is a lot of crud blocking the screen and the pump can only pull enough fuel through it for 6 Psi

If anyone has any experience with fuel pumps, let me know if I'm on the right track.

 

Is there anywhere else in the fuel line that there could be a blockage? Besides the screen and the inline fuel filter.

 

the lines themselves yes

 

There are two common tests for an EFI fuel pump. One is an open flow test. This will point out any restriction in the lines, a clogged filter or a weak pump. You perform this test by first disconnecting the rubber portion of the supply line from the fuel pipes at the left front of the engine, and placing the end of this rubber line into a fuel resistant container. Then connect 12v to terminal G of the aldl tro activate the pump. The disconnected line should emit a healthy stream and pump a 1/2 gallon of fuel in about a minute. If the stream is weak andf flow is well below 1/2 gallon per minute, disconnect the line from the tank to the filter and repeat the test there. If flow improves dramatically, replace the filter and try again at the engine.

The second test of the EFI fuel pump is a dead head pressure test. To perform this test, reconnect all porttions of the supply side of fuel system and use pinch off pliers to restrict flow through the rubber portion of the return line at the front left corner of the engine. With the pump running and this hose pinched shut, fuel pressure should reach 100psi. If it is way short of this point, you have a bad pump. If the pump passes both of these tests, suspect your pressure regulator. The diaphram is probably ruptured. Remove the vacuum line from the regulator and run the fuel pump. Does fuel emit from the vacuum fitting?

 

I will give these a try. Thanks.

 

So I don't know why I didn't ask this before but, what should the fuel pump sound like?I would think it would sound like a hi pitched whine, but mine sounds more labored.

 

It should be fairly high pitched and not too loud. The tests I detailed for you should point to any trouble.

 

Have you checked the the FPR yet? 6 psi and rich smell, possibly bad diagphram in regulator which will cause fuel to mainline into the intake....flooding, and low fuel pressure at the port. Reason it will start up after a few minutes setting is due to fuel evaporating enough to allow it to spark a bit.

 

I replaced the FPR about six months ago. My fuel pump is pretty loud and not very high pitched.

 

Use a voltmeter to test power at the pump connector just above and forward of the tank.(You'll need to raise and support the car for this.) With the pump running, measure DC voltage between the pump power and ground wires. GM generally uses gray for pump power and black for ground. Refer to your diagram for wire colors and connector pins. Reading should be atleast 10v. If less, check condition of wiring and connections.

 

So it was the fuel pump!
I went ahead and dropped the tank this last weekend, which was not nearly as scary as I thought it would be, got the pump and tank back in today after work, put 5 gallons of gas, turned the key, heard the pump prim which sounded much higher pitched and quieter.
The FP gauge said 20psi at first but then I used the bleeder valve to get the air out of the line, then I went ahead and started the engine and it fired up right away! I looked he FP gauge again and was at just under 40psi!
So I think the starting problem is fixed.
The only this is, the fuel pressure in the rail starts to fall after the engine is turned off.

 

The drop in pressure after shut down is okay. The general rule is 20 seconds to fall to 0. Any less than 20 seconds points to a problem in either an injector, the regulator, or the check valve in the pump. Glad to hear your problem is solved.

 

That's good to hear.
Hey, and thanks to everybody for the responses, they were all helpful.