1989 Ford Bronco - stumbles on start

Read under difficult starting.


The difference between 35 and 40 PSI of fuel pressure is not the cause of this problem. What I was wondering if if the fuel pressure dropped to zero or close to it after several hours.

Moving the TFI module to the fender won’t help anything if the module has a pre-existing problem.

Back in the day I owned several TFI cars. After a couple of module failures (this usually happens in summertime) what I did is mount the module on pieces of finned aluminum heatsinks. I then mounted the modules inside the air filter box before the air filter with screws and self locking nuts… I then extended the pigtail wire harness to the relocated modules.
This means that whenever the engine is running the incoming air is keeping that module cooled down and never had another TFI module problem ever.

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Yeah, but then the electrical signals had to go all the way to the air box to reach the TFI module, and then all the way back to the ECM to fire the coil! Didn’t the delay from the electricity traveling so far cause retarded timing? :laughing: :laughing: :laughing:

(that’s a joke for people who didn’t know)

I moved my ICM to the fender with heat sink—installed a hotter coil made for the EEC-IV computer system--------------takes care of that issue–only retard is the driver-! (Added to joke)

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I bought a cheap Chinese timing advance module off of eBay to offset the retarded timing due to the longer wiring pigtail…(might be joking…)

Offhand, the problem points to a loss of fuel pressure which is usually the check valve in the fuel pump followed by a leaking fuel pressure regulator or fuel injector. If fuel pressure goes to zero after sitting for quite a while my first suspect would be fuel pump.

Have you tried pulling diagnostic codes? This is OBD I and there are some codes that can be set by the TFI module. Namely loss of SPOUT or PIP signals, etc. A CEL may not be illuminated when this happens.

It’s normal for the residual fuel pressure to bleed down to 0 PSI over time.

Each manufacturer has a spec for how long it should take.

So don’t think the fuel pump is bad when this occurs.


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In my 89 xlt 351W, I had no apparent retard issue using an ICM moved from the distributor to the fender–The PIP signal works ok—I know that the EEC-IV computer does the starting receiving certain sensor input. Mine is 33 years old and although it is old, still a hearty computer–but hey, condensers and diodes do go. I’m thinking that that is my main issue in starting–the fuel pressure is 35 pounds and Ford says 15 seconds to start bleeding down. I saw a big difference changing the ICM to a better one, doesn’t stumble between 200 and 300 rpm and hang there–it does a steady 500 and will increase to above 700 and then back down to 700 idle. The racing coil I put in there was designed to work with the EEC-IV Ford designed computer and changes secondary from 25,000 V to 48,000 V—it runs extremely smooth, very noticeable. At 204,000 miles, I did have timing stretch—A knowledgeable mechanic adjust the timing to compensate for that----where the Bronco likes it–so forget 10 degrees before–mine now says TDC–but it really isn’t firing at TDC. Made a tremendous difference on performance–more pep, great transmission shifting. Now I’ll have to change the differential ratio as I have 32-1150-r15 tires on it and really should do the front also but, don’t have the money.

My Bronco Hot Starts extremely fast so no problem in that area. With Arizona temperature in the 3 digits in summer, I’m sure it effects a slower so called, cold start with like 105-115 degrees. I’ve noticed in around January, February–the cold start is pretty much fast starting—but—I have not had anyone tell me anything about that as the MAS is one of the things and coolant temp also that the computer uses for cold start–meaning below–??? what temperature would you think you will see a start difference???

One idea, when it won’t start properly, test if holding the accel pedal to the floor during cranking has any effect.

I think there is a lot of erroneous info in your posts.
First off; forget this 25 and 48 K volts with racing coils business. In an engine with normal compression, good plugs/wires, etc the voltage needed for the spark to jump a plug gap will likely never exceed 10 K volts and not likely ever hit that number.
If the secondary voltage jumps to 15 K volts or something in that range then there is a bad plug or wire issue. Lowered voltage (3 or 4 K volts) means low compression, bad injector, plug gap too narrow, etc.
Things like this can be seen in action on an oscilloscope.
The same principle applies to say a 140 amp alternator. That alt. will never put out 140 amps although it can be made to…for a minute. Then followed by a fire under the hood.

The coolant temp sensor is not going to make that much difference on cold starts.

Eyeballing the ignition timing on one of these is a bad thing to do; chain stretch or not. The timing MUST be set with the SPOUT connector disconnected. Offhand, sounds like the timing is advanced by 10 degrees; normal when the SPOUT is not disconnected. Extra advance will perk any car up but the downside is that it would be very easy on an extended highway run for that extra advance to start eating up pistons; followed by a bang at some point.
In the past I’ve purchased on the cheap several nice cars whose engines were ruined by this kind of faux pas. Bad for the car owner; good deal for me.

I’m aware that fuel pressure will bleed off after a bit. However, if it bleeds off to zero then there will be a starting issue. There’s a difference between bleeding down to zero as compared to say 10 or 15 PSI.

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Auto mechanics get their daily drivers for free, plumbers get their home’s hot water heater for free, appliance repair folk get their refrigerators and washing machines for free. Goes w/the job, fringe benefits! :slight_smile: Seems like a fair deal to me.

What does this mean @ok4450 ? A brief tutorial on Ford ignition systems of that era would be helpful.

“The timing MUST be set with the SPOUT connector disconnected.”

That means that the SPark OUTput signal at the ECM needs to be disconnected to make sure the car is in base timing mode.

Essentially the same thing as disconnecting the vacuum advance vacuum hose from the distributor before checking/adjusting timing on an ancient car, say an early 70’s Ford 302. If anyone still drives one of those… :grinning:

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Not true.

The fuel pressure itself will bleed down to 0 PSI.

But the anti drain back valve will maintain a fuel column in the fuel system.

Then when the ignition switch moves to the run position before the engine is started, the fuel pumps runs for second or two to immediately build fuel pressure.

That’s because you can’t compress a liquid.

Now when the anti drain back valve fails in the fuel pump, the fuel column is allowed to drain back into the gas tank.

This is when we get the complaints about hard starting after the vehicle has sat.

We tell them to cycle ignition switch a half dozen times so the fuel pump can reprime the fuel line and fuel rail(s) with fuel and to build the proper fuel pressure so the engine will start.

But the fuel pressure will eventually bleed down to 0 PSI.


There’s not much to tell in regard to the TFI module ignition systems. It’s a very simple system. Leaving that SPOUT connector untouched while setting the timing will throw it off by approx. 10 degrees. I think the OP needs to rethink that issue before he ends up with a wiped engine. Low speed, around town won’t likely be a problem. A highway trip could well be especially if the EGR system is not operating properly.

I’m fully aware a liquid cannot be compressed. If the pressure in the line is zero due to bleeding off then that can very well cause hard or slow starting, stumbling, and so on until the air is burped out. Offhand, sounds like our thinking is the same.

The link provided is in regard to CIS injection and CIS is not even in the same universe as “normal” fuel injection systems. Everything about CIS in regard to leaks, starting problems, causes, and components is completely different. Even the fuel pressure test gauge and how the pressure tests are performed are completely different.