Hi, First let me give a summary of my problem. When my Bronco has been sitting for 6-8 hours, it starts right up with no problems. However, if the truck has been sitting for an hour or so after being driven for a while, it takes 5-6 seconds of cranking to get it to start. When it does start, the smell of gas coming from the exhaust is quite strong. Once the engine is running, it runs very well and has yet to ever miss a beat.

I think the problem is caused by a leaky injector flooding out the cylinder, making it hard to start. Here's my theory.....it starts right up when it's been sitting for a long time because the residual pressure left in the line has leaked out completely and the gas in the cylinder has evaporated. When the truck sits for an hour or so, the gas is still leaking into the cylinder which floods it out making it difficult to start. To reinforce this theory, there is a strong smell of gas coming from the air inlet.

I've done the various fuel system tests(engine off pressure test, engine running pressure test, static pressure leakage check, overpressure test, underpressure test, etc.) per the shop manual and everything checks out, including the system pressure holding steady at around 38 psi for over a minute. The shop manual says everthing in the fuel system is ok, but the smell of gas and the starting problem makes me think otherwise.

What do you guys think? Could the leak in one of the injectors be small enough to allow gas into the cylinder while still passing the static pressure leakage test?

I've heard the TFI module is the weak point of the Ford system and that it can cause weird ignition problems when they heat up, so I've already ordered a new one from Ford. My unit is remotely mounted on the drivers side inner fender to minimize heat but it still gets pretty hot to the touch. What else could it be?

 

HI, OK, I don't know if this will help. I changed my 89 Bronco 351W from it's old system to a new FOrd Racing MAF system. It worked fine for a few months. Then one day it decided to fuel flood. I have called the Ford guys and they say it has to be something other then the MAF system.
I've replaced everything trying to "cure" the problem. No good results.
My thinking is the computer is "off". But, until I do the engine rebuild this weeked, I will not know.
Now on to a single injector. Pull the plugs. If one is a leaker it will be wet with gas. If all of them are leakers then there is a major problem. It could be the pressure regulator, could be all sorts of things.
If you take the injectors to a shop that has the equipment to test them that is one thing to try. But expect to pay $ for that.
Sorry not to have good news. But, I'm trying to figure out the flood problem too. Actually, have asked here before, and nobody has a "good" answer.
Bruce (Big Red Bronco)

 

Yeah, I realize there are a lot of variables here, that's why I did all the tests that test the fuel pump, fuel pressure regulator, check valve, etc. to see if the tests would give me some clue. It passed every test I threw at it!!

I've also already pulled each plug to see if they could give me some clue but they were all uniform and none of them were wet.

I take very good care of my Bronco and it just bugs me when I can't find a solution....even with the shop manual!!!!

 

do you hear any air leaks, maybe your intake gasket that goes between the plenum and lower intake is shot or is soaking up gas causing the smell. also you may have an electrical problem like your plugs arent getting enough spark to burn the fuel properly. so maybe your coil is going out or you have some bad plug wires

 

I just changed the plugs, cap, rotor, and wires. I checked the coil primary and secondary resistance, primary circuit continuity check, and the voltage going to the coil and it passed all tests.

One thing I did check yesterday that wasn't quite right was the fact that I'm getting around 3.5 mV of stray voltage at module harness connector pin 2 but the shop manual says there should be absolutely no voltage. The corrective measure is to "service short to power in harness and perform general ignition checks."

Anyone know how to do that? Ford tech guys please chime in......

 

Alright, just an update and a couple of quick questions for those in the know. I decided to leave the fuel pressure gauge on the fuel rail for awhile to see how fast the pressure would leak down even though the system passed the static leakage test.

I got 38 psi when I shut the engine off. After about 1/2 an hour, the fuel pressure had dropped 20 psi and the smell of gas was quite strong from the air inlet tube.

This seems like excessive leakage to me. Isn't that more than enough leakage to flood out a cylinder and cause the hard start condition I'm having? Is it time for new injectors?