Wiring gremlins / FiTech

[tk1218]

Background

73 bronco 302, fitech with fuel pump reservoir, Dakota digital, classic auto air, Petronix replaced point and new painless 28 circuit harness.

Issue

Starts, runs and then stalls after about 10 minutes. It appears that the fitech fuel pump is not getting power after it gets warm. After it cools off it starts, but will keep stalling. Also noted that some other electrical is not working when the stalling starts to happen

A bit baffled as the painless harnesses are as close to plug and play as you can get. Here are a few other details on the wiring

Used accessory 2 b+ yellow for fitech constant power
Used accessory 3 b+ red/yellow for Dakota constant power
Used harness heater wiring to power classic auto air

Used electric choke wire white/ black for fitech switched power
Used accessory 8 orange/white for low pressure fuel pump - mechanical fuel pump delete
Used accessory 9 pink for Dakota switched power

It’s almost like something is getting hot and taking out many of the circuits until it cools off

Any advice or insight would be appreciated

 

[fluffybunny]

What low pressure fuel pump are you using?

 

[.94 OR]

When I had the power commander on mine it would cause hot run issues. Finally swapped to a 23 gallon tank with high pressure pump. It ran good after that.

 

[DirtDonk]

Couple of things.
First of all, it does seem you have an electrical issue because an electric fuel pump not pumping would have nothing to do with other accessory power going out. But for the fuel reservoir, are you running a return line, or not?
Without a return line the electric pump reservoirs often seem to run hot. Lots of issues when we first started using those with the, FiTech, and Edelbrock wasn’t much better.
Any time you do plumb in the return line however, many of those problems seem to go away.

Now to your electrical, you’re using a couple of incorrect circuits for things that are important.
I’ll have to go back and reread it just to see what’s going on, but you need to measure voltage in some areas.
Mainly the white with black stripe wire from the alternator does not have correct power. And it is not switched. It only works when the engine is running and it does not provide 12 V DC.
So change that.

 

[DirtDonk]

Starts, runs and then stalls after about 10 minutes. It appears that the fitech fuel pump is not getting power after it gets warm.

Are you powering the fuel pump module from a relay, or straight off the wire from the harness?

Also noted that some other electrical is not working when the stalling starts to happen

Which other circuits exactly?

Used accessory 2 b+ yellow for fitech constant power
Used accessory 3 b+ red/yellow for Dakota constant power

And verified with a voltmeter that they both had constant power. Correct?

Used electric choke wire white/ black for fitech switched power

Change that as mentioned.

Used accessory 8 orange/white for low pressure fuel pump - mechanical fuel pump delete.

Are you running this through a relay, or just directly off that wire to the pump?
What gauge is that wire, and where is the pump mounted?

When it stops running, have you checked for spark?
Even though it does sound like a potential fuel problem, don’t ignore spark.

And as a general rule, did you add extra ground circuits to your vehicle?
Specifically, battery to body, engine to body, engine to frame, body to frame, throttle body to Intake manifold, and any others that you happen to think about.
Also, have you been reading the discussions here over the years about RFI issues with throttlebody set ups that have the computer right next to the distributor? If not, that makes some interesting reading.

 

[tk1218]

What low pressure fuel pump are you using?

Edelbrock from Reilly auto parts, the low pressure 1. Thought about running the high pressure 1

 

[tk1218]

Couple of things.
First of all, it does seem you have an electrical issue because an electric fuel pump not pumping would have nothing to do with other accessory power going out. But for the fuel reservoir, are you running a return line, or not?
Without a return line the electric pump reservoirs often seem to run hot. Lots of issues when we first started using those with the, FiTech, and Edelbrock wasn’t much better.
Any time you do plumb in the return line however, many of those problems seem to go away.

Now to your electrical, you’re using a couple of incorrect circuits for things that are important.
I’ll have to go back and reread it just to see what’s going on, but you need to measure voltage in some areas.
Mainly the white with black stripe wire from the alternator does not have correct power. And it is not switched. It only works when the engine is running and it does not provide 12 V DC.
So change that.

Yes, running a return line. It’s the fitech version that includes the reservoir and high pressure fuel pump

 

[tk1218]

Are you powering the fuel pump module from a relay, or straight off the wire from the harness?

Which other circuits exactly?

And verified with a voltmeter that they both had constant power. Correct?

Change that as mentioned.

Are you running this through a relay, or just directly off that wire to the pump?
What gauge is that wire, and where is the pump mounted?

When it stops running, have you checked for spark?
Even though it does sound like a potential fuel problem, don’t ignore spark.

And as a general rule, did you add extra ground circuits to your vehicle?
Specifically, battery to body, engine to body, engine to frame, body to frame, throttle body to Intake manifold, and any others that you happen to think about.
Also, have you been reading the discussions here over the years about RFI issues with throttlebody set ups that have the computer right next to the distributor? If not, that makes some interesting reading.

High pressure pump powered via supplied relays with the kit

When it heats up and stalls t/s switch not working + hazards and Dakota freezes up. High pressure fuel pump and only 10.6 volts to the distributor

Constants are verified as b+ when cold, have not verified after it stalls (was on the side of the road)

The electric choke wire from the painless harness is hot in start and run

High pressure has a relay and supplied wire from kit. Low pressure is through an on off switch with 14 gauge wire. Low pressure is working in all situations

Haven’t ch3cked for spark when not running but assume it’s not sparking at 10.6 volts

Extra grounds have been added. No ground from throttle body to intake

Computer is on the drives kick panel above the ebrake

Thanks for your reply and questions

 

[DirtDonk]

When it heats up and stalls t/s switch not working + hazards and Dakota freezes up.

Interesting. What do all of these have in common by chance?

High pressure fuel pump and only 10.6 volts to the distributor

Distributor is fed through one of the normal "IGN +" wires from the harness? Or something else? Is it the same reading at the battery?
Where else do you read that low voltage? Without having a resistor installed (which you would not with this setup I don't think) you should be seeing full battery voltage at almost all points.

Constants are verified as b+ when cold, have not verified after it stalls (was on the side of the road)

Yeah, I hear ya on the less-than-ideal testing circumstances. But better sooner rather than later to find out.
Check as many points as you can not only for the presence of power, but how much it has compared with what's at the battery.

The electric choke wire from the painless harness is hot in start and run

now that's interesting as well. The Bronco harness is supposed to mimic the factory setup in most spots. And they do that in about 90% of the circuits, other than adding fuse protection to them and by necessity re-routing some of them. But the stator wire should be running from the alternator directly up to the carburetor (when using a carburetor that is) without a fuse or any interruption.
I guess they felt in this case that nobody was going to be using a factory carburetor and did not need the old wiring scheme. So changed it to a more direct-from-battery setup.
Still, no need for it to be hot in START either, since it's not a mission critical component. And usually the factory did not want the choke powered up until the engine was running. Personally though, I always thought converting to keyed power was a good plan for chokes. That way if you were at high altitudes and an engine was prone to flooding while trying to start (an all too common problem way back when) you could just turn the key on for a minute and open the choke.
We used to use rubber bands to do the same thing with factory chokes. I guess that's not necessary anymore...

High pressure has a relay and supplied wire from kit. Low pressure is through an on off switch with 14 gauge wire. Low pressure is working in all situations

Good to know. When the low pressure pump is working, you have verified that the high-pressure pump is DOA at that point? Not working at all, or just not very well?

Haven’t ch3cked for spark when not running but assume it’s not sparking at 10.6 volts

You can get plenty of spark out of most normal ignitions with as little as 4v. Well, by "plenty" I mean you can get a spark. Should be more than 6v to get decent spark, but the original ignitions were running on 7v to 9v typically after warming up. But Broncos could still run on 5-6v and you didn't even know it was having trouble at that point.
So your 10.6v is not optimum for a system that does not utilize a resistor, but it's not right either when you are supposed to be at 12 to 15 volts!

The Pertronix distributor module wants the full voltage, but what coil are you using? Some will prefer and be perfectly fine with full voltage, while others will overheat if you don't have a resistor. If yours is meant to be in the 6-9 range, maybe that's part of your problem.
Even an overheating coil will not kill other components. It'll stop the engine from running, but it won't stop other accessories.
Anything else connected to the ignition components anywhere else?
Also, do you have a tachometer by any chance? If so, disconnect it while doing your testing to make sure it's not part of the problem.

Extra grounds have been added. No ground from throttle body to intake.

You should add one. It's not a 100% cure-all for problems, but enough of them have been reported, then fixed by members here, to warrant adding a small ground strap/wire between one of the attaching bolts and the engine. Maybe not even the intake manifold, but perhaps to a common grounding point anywhere.
And yes, it should be sufficiently grounded (bonded) to the rest of the system through the attaching points of the throttle-body to the intake, then the intake through the engine block, then to the battery through the main ground. But adding an additional one has been proven to help in some cases.
At least with RFI, but not with other circuits dropping out.

Computer is on the drives kick panel above the ebrake

What computer? What EFI system are you running?

Paul

 

[tk1218]

Interesting. What do all of these have in common by chance?

Distributor is fed through one of the normal "IGN +" wires from the harness? Or something else? Is it the same reading at the battery?
Where else do you read that low voltage? Without having a resistor installed (which you would not with this setup I don't think) you should be seeing full battery voltage at almost all points.

Yeah, I hear ya on the less-than-ideal testing circumstances. But better sooner rather than later to find out.
Check as many points as you can not only for the presence of power, but how much it has compared with what's at the battery.

now that's interesting as well. The Bronco harness is supposed to mimic the factory setup in most spots. And they do that in about 90% of the circuits, other than adding fuse protection to them and by necessity re-routing some of them. But the stator wire should be running from the alternator directly up to the carburetor (when using a carburetor that is) without a fuse or any interruption.
I guess they felt in this case that nobody was going to be using a factory carburetor and did not need the old wiring scheme. So changed it to a more direct-from-battery setup.
Still, no need for it to be hot in START either, since it's not a mission critical component. And usually the factory did not want the choke powered up until the engine was running. Personally though, I always thought converting to keyed power was a good plan for chokes. That way if you were at high altitudes and an engine was prone to flooding while trying to start (an all too common problem way back when) you could just turn the key on for a minute and open the choke.
We used to use rubber bands to do the same thing with factory chokes. I guess that's not necessary anymore...

Good to know. When the low pressure pump is working, you have verified that the high-pressure pump is DOA at that point? Not working at all, or just not very well?

You can get plenty of spark out of most normal ignitions with as little as 4v. Well, by "plenty" I mean you can get a spark. Should be more than 6v to get decent spark, but the original ignitions were running on 7v to 9v typically after warming up. But Broncos could still run on 5-6v and you didn't even know it was having trouble at that point.
So your 10.6v is not optimum for a system that does not utilize a resistor, but it's not right either when you are supposed to be at 12 to 15 volts!

The Pertronix distributor module wants the full voltage, but what coil are you using? Some will prefer and be perfectly fine with full voltage, while others will overheat if you don't have a resistor. If yours is meant to be in the 6-9 range, maybe that's part of your problem.
Even an overheating coil will not kill other components. It'll stop the engine from running, but it won't stop other accessories.
Anything else connected to the ignition components anywhere else?
Also, do you have a tachometer by any chance? If so, disconnect it while doing your testing to make sure it's not part of the problem.


You should add one. It's not a 100% cure-all for problems, but enough of them have been reported, then fixed by members here, to warrant adding a small ground strap/wire between one of the attaching bolts and the engine. Maybe not even the intake manifold, but perhaps to a common grounding point anywhere.
And yes, it should be sufficiently grounded (bonded) to the rest of the system through the attaching points of the throttle-body to the intake, then the intake through the engine block, then to the battery through the main ground. But adding an additional one has been proven to help in some cases.
At least with RFI, but not with other circuits dropping out.

What computer? What EFI system are you running?

Paul

 

[tk1218]

Don’t really see any reason or relation to the issue which usually means a ground issue

Yes on the ignition wire in the harness. When it’s cooled of the battery and coil read 12.5 at start. When running it’s around 14. When it stalls battery is 12.5 and coil is 10. Some of the accessory wires (switched and b+) have no voltage when it stalls plus the others noted above.

Hopefully it will stall in the driveway next time and I can test all the circuits

Yes, high pressure pump has no voltage when it stalls, low pressure still working

Flame throwing coil, nothing else connected to the ignition since the harness has all those extra circuits. Dakota has a built in tach

It’s a fitech go street 400

Thanks

 

[tk1218]

Can something shorting in the fitech potentially take out the other circuits?

I had a bad starter once take out the entire system until I disconnected it from the solenoid

 

[DirtDonk]

Can something shorting in the fitech potentially take out the other circuits?

As far as I know, no, that’s not possible, unless they are directly connected to each other.
Which is why I asked that question earlier about what might be sharing a circuit.
However, even then, it seems pretty far-fetched.

Again though, what computer is on the kick panel? The main FiTech ECU is mounted to the throttlebody unless something has changed recently.

 

[tk1218]

Sorry, the fitech relays are on the kick panel with the ecu connected to it