Pulling the trigger

[FrazerJames]

Hi Everyone!

I’ve been spending the last 2-3 going through an 85 Mercedes diesel wagon and couldn’t have done it without the large community supporting novices like me. So I’m VERY happy to see this awesome forum so active.

I live in St Louis, MO in one of the last truly Little Italy neighborhoods with my wife, 7yo and a huge garage.

Here’s where I’m at: In the market, generally, but have my eye set on an ‘83 base model Bronco with a 300 I6 in copper red. It’s probably overpriced, but it’s been with 1 owner and in remarkable condition cosmetically both inside and out. Where it gets tricky is that it has only 120K miles on it, but sat garaged for 12 years (the owner is nearing 90yo). A neighbor has agreed to sell it for him, threw some non-rotted tires on and got it running. Apparently it was running like a top “handles like it’s brand new”, but for some reason they decided to bypass the smog pump. Since then it seems to have an issue where it’s struggling when going uphill - they believe it’s a vacuum issue or that it needs the fuel tank flushed (they replaced the fuel pump and fuel lines).

Anyway, it’s a beautiful Bronco and I need to decide whether to jump on it. They’re asking over $10K...

I realize it will probably need any rubber replaced. Probably some upgrades to be had. I’m also concerned how well the engine can handle highway speeds. Any insight there will be great. I know it’s not a speed demon (neither is the Merc Diesel). I guess I’m looking for a good half-time speech here. LOL.

[Gary Lewis]

Welcome! We have a map (Bullnose Forum/Member's Map in the menu) and with your permission we can add you.

Little Italy in STL? Our kids used to live at Tower Grove Park, across the street from Ices, and we've been to and through The Hill many times. Is that where you live?

On the Bronco, I think it sounds like a good one. According to our page at Documentation/Driveline/Transmissions/Automatic Transmissions/Applications that Bronco should have the C6. That's a robust transmission but not good for MPG since it doesn't have an overdrive and the torque converter doesn't lock up.

As for the lack of power, I think that the truck may have the EEC-III system that controls engine timing and even the air/fuel ratio. And depending on what all they did they may have triggered limp-home mode on the ECU. Basically in that mode the ECU locks the timing to base or initial, meaning there is no advance. That kills power and economy.

You can covert from what I suspect is the TFI ignition to the more simple DS-II ignition with not much trouble and that will eliminate the ECU. Or, if what they did can be put back, you may get it going again.

[Gary Lewis]

Welcome! We have a map (Bullnose Forum/Member's Map in the menu) and with your permission we can add you.

Little Italy in STL? Our kids used to live at Tower Grove Park, across the street from Ices, and we've been to and through The Hill many times. Is that where you live?

On the Bronco, I think it sounds like a good one. According to our page at Documentation/Driveline/Transmissions/Automatic Transmissions/Applications that Bronco should have the C6. That's a robust transmission but not good for MPG since it doesn't have an overdrive and the torque converter doesn't lock up.

As for the lack of power, I think that the truck may have the EEC-III system that controls engine timing and even the air/fuel ratio. And depending on what all they did they may have triggered limp-home mode on the ECU. Basically in that mode the ECU locks the timing to base or initial, meaning there is no advance. That kills power and economy.

You can covert from what I suspect is the TFI ignition to the more simple DS-II ignition with not much trouble and that will eliminate the ECU. Or, if what they did can be put back, you may get it going again.

I missed the highway speeds question. The Broncos typically came with 3.50 gears, and with the C6 you'll be turning ~2750 RPM at 65 MPH. It should do fine on the highway. However, that's well above the "sweet spot" in RPM for the 300 six, which is about 1000 RPM lower, so it isn't going to get stellar MPG. And it may not want to run a whole lot faster as that engine doesn't like to spin all that fast - it is a great engine but is a low RPM/high torque unit.

I've not driven a 300/C6 combo so I really can't say. Perhaps someone else can? I know Matthew/Dorsai has a pickup with the 300/C6 combo, as outlined here, but he has 2.75 gears.

Maybe you need to figure out what gears that Bronco has? Decode the certification label on the page at Documentation/Specifications/Certification Label. Or go directly to Documentation/Specifications/Axle Ratios.

[FrazerJames]

I missed the highway speeds question. The Broncos typically came with 3.50 gears, and with the C6 you'll be turning ~2750 RPM at 65 MPH. It should do fine on the highway. However, that's well above the "sweet spot" in RPM for the 300 six, which is about 1000 RPM lower, so it isn't going to get stellar MPG. And it may not want to run a whole lot faster as that engine doesn't like to spin all that fast - it is a great engine but is a low RPM/high torque unit.

I've not driven a 300/C6 combo so I really can't say. Perhaps someone else can? I know Matthew/Dorsai has a pickup with the 300/C6 combo, as outlined here, but he has 2.75 gears.

Maybe you need to figure out what gears that Bronco has? Decode the certification label on the page at Documentation/Specifications/Certification Label. Or go directly to Documentation/Specifications/Axle Ratios.

Hi Gary!

Yep, I’m on The Hill! Right in the center of it. Across from DiGregorios Italian Market to be exact! Love this neighborhood, but Tower Grove is great too!

Interesting thoughts on the ECU. Does the “limp home” reset? The seller says they’ll drive for 5 minutes, it’ll start to fall on its face, and then if they pull over and wait a bit, it’ll drive normally again.

I’ll find out about those gears!

 

[Gary Lewis]

Hi Gary!

Yep, I’m on The Hill! Right in the center of it. Across from DiGregorios Italian Market to be exact! Love this neighborhood, but Tower Grove is great too!

Interesting thoughts on the ECU. Does the “limp home” reset? The seller says they’ll drive for 5 minutes, it’ll start to fall on its face, and then if they pull over and wait a bit, it’ll drive normally again.

I’ll find out about those gears!

Cool! We used to drive close to your house as we took Shaw through the neighborhood.

No, the limp-home mode won't reset. That sounds like a fuel problem. I had a similar problem when the rubber hoses turned to mush on two of my trucks. Apparently the old hose material doesn't like ethanol and in one case it was so sticky that I balled the hose up and it stayed that way.

Rubber was used between the tank and the hard line on the frame, and again from the hard line to the fuel pump. If it gets porous, as mine did, it'll let air in and that kills the vacuum that the pump uses to move gas. But it doesn't do it instantly, it takes time and I got about 20 minutes of driving before it couldn't pump any more gas.

I bought new fuel line in bulk that is ethanol rated and changed out all of the hoses. Problem solved.

That may not be your problem, but it might be.

[FrazerJames]

Cool! We used to drive close to your house as we took Shaw through the neighborhood.

No, the limp-home mode won't reset. That sounds like a fuel problem. I had a similar problem when the rubber hoses turned to mush on two of my trucks. Apparently the old hose material doesn't like ethanol and in one case it was so sticky that I balled the hose up and it stayed that way.

Rubber was used between the tank and the hard line on the frame, and again from the hard line to the fuel pump. If it gets porous, as mine did, it'll let air in and that kills the vacuum that the pump uses to move gas. But it doesn't do it instantly, it takes time and I got about 20 minutes of driving before it couldn't pump any more gas.

I bought new fuel line in bulk that is ethanol rated and changed out all of the hoses. Problem solved.

That may not be your problem, but it might be.

The seller says they replaced the pump and the lines, but maybe they didn’t get all of them... He suggested that a fuel tank flush might fix it, but I’m not so sure...

I’ve been going through that thread on the truck. Now I’m getting psyched!

Are you near St Louis still?

[FrazerJames]

The seller says they replaced the pump and the lines, but maybe they didn’t get all of them... He suggested that a fuel tank flush might fix it, but I’m not so sure...

I’ve been going through that thread on the truck. Now I’m getting psyched!

Are you near St Louis still?

And I forgot to say, yes, please feel free to add me to the map!

[FrazerJames]

And I forgot to say, yes, please feel free to add me to the map!

Also, a few terrible pics of the engine for reference. This will be the first gasoline engine I’ve worked (carbureted too) so I’m starting to dive into the specifics. If there’s anything notably off for those who know these just based on the pics, I’ll know I’m probably beyond my initial skill level. I’m great at following directions, but not very good at identifying or troubleshooting.

[Gary Lewis]

The seller says they replaced the pump and the lines, but maybe they didn’t get all of them... He suggested that a fuel tank flush might fix it, but I’m not so sure...

I’ve been going through that thread on the truck. Now I’m getting psyched!

Are you near St Louis still?

No, we are basically in Tulsa. It was our son and his family that lived there. But they moved about three years ago.

I don't think a fuel tank flush will fix it. I'm guessing they didn't replace the hose from the tank to the hard line. It is a pain to get to, but you should be able to lower the tank via the straps enough to get to it. Or put a board and a floor jack under it to lower it just enough to reach up there.

Having said that, the TFI ignition might be able to break down with heat and give a poor spark. It is notorious for failing due to heat, but I think the failure mode is usually from "on" to "off" rather than a weak spark. But you could test for that when it fails by checking for a weak, yellow or red, spark.

If it is the TFI then you need to decide your path forward. As said, they were notorious for failing due to heat. Ford later moved the module to the fender to get it away from the heat of the engine, so you could do that.

But, that would still use the ECU and feedback carb, assuming you have them, and you may want to eliminate them and go with a non-feedback carb and DS-II ignition.

I'm just laying out options so you don't run off and throw money at it and find you might have wanted to go a different way.

[FrazerJames]

No, we are basically in Tulsa. It was our son and his family that lived there. But they moved about three years ago.

I don't think a fuel tank flush will fix it. I'm guessing they didn't replace the hose from the tank to the hard line. It is a pain to get to, but you should be able to lower the tank via the straps enough to get to it. Or put a board and a floor jack under it to lower it just enough to reach up there.

Having said that, the TFI ignition might be able to break down with heat and give a poor spark. It is notorious for failing due to heat, but I think the failure mode is usually from "on" to "off" rather than a weak spark. But you could test for that when it fails by checking for a weak, yellow or red, spark.

If it is the TFI then you need to decide your path forward. As said, they were notorious for failing due to heat. Ford later moved the module to the fender to get it away from the heat of the engine, so you could do that.

But, that would still use the ECU and feedback carb, assuming you have them, and you may want to eliminate them and go with a non-feedback carb and DS-II ignition.

I'm just laying out options so you don't run off and throw money at it and find you might have wanted to go a different way.

I think I’d definitely upgrade to the DS-II and non-feedback carb. At this point, I just need to get it home. It’s 2 hours away so I’m weighing my options.