fastboats380

Hello everyone this is my first post, I have a 91 RS 305 and it was running pretty good, I shut it off and it wouldn't start, I was in a rush so I figured just to eliminate spark id try either, it fired up and died, I did it again and the only way it would stay running was if I was pumping gas pedal ALOT, if I held it in ANY spot it would die and upon pumping it, it would backfie flames through the Throttle body!! Please help! Thank you and I gotta say this site ROCKS!

fastboats380

I guess ill start throwing parts at it... Starting with Fuel pressure regulator

J-money

Have you tested your ignition control module?

Schurkey

Flames out the intake (intake backfire) is typically due to lean fuel mixture.

I'd be looking at fuel pressure, clogged injectors, etc.

As always, a scan tool and the data stream are your friends.

fastboats380

It has Fuel Pressure up to the TB, It only sprays fuel when im pumping the throttle, its really weird... I installed a TPS and a Ignition Control Module.. What else should I try? im about to say EFF it and light it on fire..

Ron U.S.M.C.

I cracked the small plastic vacuum line going to the MAP sensor when setting timing.
I thought I could start it and drive to an auto parts store and buy a piece of hose to patch it.
I had a friend try to start it and it shot what ever it could a few feet into the air like it exploded. There was a cloud but did not see any flames. It happened to fast.
What I'm getting at is its close to what you have going on.
Its amazing what a little sensor can do.

fastboats380

So I tinkered some more, watching the injectors they only spray fuel between 2000-2800 rpms so im guessing its either the pressure regulator or pump witch is brand new! I pulled apart the regulator and I didnt see anything that looked bad but all it looks like to me is a diaphragm but IDK...

1983Chimaera

Check your fuel system thoroughly, including the fuel intself (not old/brown/contaminated), the tank (debris in the tank, clogged/damaged fuel strainer, etc), check the fuel filter, check fuel pressure at the engine (you can rent pressure gauges at most of the big chains now), and verify the injectors are good (you can rig up a tester pretty easy with a 12V battery, some wire, and a fuel pump). If everything on the fuel system side is good then check the ignition side; cap, coil, wires, plugs, and make sure you have good spark. You might have crossfire inside the cap from a crack or carbon tracing. If all that is good THEN start throwing parts at it.

fastboats380

everything in the ignition is brand new, cap, rotor and module.. the car did sit for awhile, 2-3 years, so it does have some old fuel but I topped it off and probably put 75 miles on it before this issue started..

1983Chimaera

2-3 YEARS??? Ok, so I'm going to assume your fuel system is full of varnish at this point and say pull it apart and start cleaning. You have a new pump, but you need to get it out of that junk before it gums up. Your injectors are probably half clogged as well.

Just putting new gas on top of fuel that old will not help, if anything it will just break free chunks of things you'ld really rather not get into more sensitive parts of the system. Next time drop and clean the tank.

fastboats380

I have had the entire TB apart and everything is cleaner than clean, ill check everything else tomorrow again

Schurkey

Do you have spark when you don't have fuel spray?

I'm starting to think "weak pickup coil", the ECM doesn't get a crank signal at low RPM, so it doesn't trigger the injectors or the ignition.

What does the scan tool show for cranking RPM?

tealman92

How about the fuel filter?

fastboats380

I dont have a OBD1 scan tool, when my MAC guy comes today I will see if he has somthing for our scanner at work

fastboats380

I would assume it hs spark since it will run if sprayed

1983Chimaera

I still recommend you clean every last bit of old fuel out of that system before proceeding. Once you've removed it and replaced it entirely with fresh gas, a clean filter, clean fuel strainer, and made sure the fuel lines and injectors aren't clogged, then you can troubleshoot the rest of the system. Otherwise you're just running in circles.

fastboats380

Ok so I put a NEW Distributor in it, started it and it ran GOOD but I had a leaky injector oring so I went to the store and bought a rebuild kit, and now the damn POS is doing the SAME thing as before!! I am losing my F*@&ing MIND!! any other Ideas that could be causing this? Unless for some reason somthing is frying the trigger in the distributor I give up and the POS is either getting a new CARB engine wich was the plan cause im eventually building a 10.5 draq car out of the POS or the POS is going down the road...

Schurkey

So...you'd rather swap engines or sell the vehicle rather than FIND A SCAN TOOL and try to tackle this logically?

You unplugged the old distributor, plugged in a new one, and you confirmed that it ran "GOOD". This largely although perhaps not completely rules-out a defective ignition coil, defective fuel pump, defective pressure regulator, stuck or plugged injectors, defective injector harness, fouled plugs, defective or crossed plug wires, wildly improper timing advance...etc. I'd be looking for wire harness problems at the distributor/coil. I'd start this procedure by looking for the RPM readout on a scan tool while cranking, because if the computer is getting a proper AND CONSISTENT distributor reference signal, you could just about rule out the distributor as contributing to the problem. Assuming you can get the thing lit again, the rest of the data stream may yield clues, too.

But don't let me stop you. Feel free to re-engine the vehicle, or dump it at a loss.

fastboats380

I understand what your saying but I cant find a OBD1 scan tool..... I also thought of somthing, I think the way my injector was leaking ALOT from the oring it was running off what was pouring into the TB.. IDK this is my daily driver for the most part. I am having it towed to a shop today