runs untill its warm (video)

[UndeadBronco]

87 Bronco II I got working finally by replacing the TFI and it worked for about a week with no porblems. Now the weather has gotten a bit hotter and it will die once it gets to normal operating temp. Since its almost summer time now it reaches normal temp much faster so its basically undriveable now. It still starts right up every time on the 1st try and runs great untill it gets warm enough. It will go about 5 miles on a 90 degree day before it stumbles and dies. It will start right back up though but only to die again. When it was/is 70ish degrees out I could drive it all over town with no problem. So what could be causing it to die only when it gets wared up? I'm told by my girl that its using about 1 quart of coolant per day when she drives it. I havent looked at it to trace the leak yet though and no matter how many times I ask her to she only opens the hood each time before she drives it to put coolant in. So many projects its hard for me to find the time.

[hames57]

The ignition modules are classic failure modes for the Bronco. The only good solution I've found is to remount the ignition module out of the heat. I assume yours is mounted on the distributor? If so, it would seem that the biggest culprit is the ignition module. When you replaced it did you goop is really good with the heat transfer white silicon stuff that was supplied with your new module? Heat transfer is absolutely critical for the survival of those modules.

[tekatlarge]

You may not have a bad TFI! You may have a bad pick up sensor inside the distributor.. Before you buy another TFI replace the sensor in the Distributor.

[UndeadBronco]

Yea, when I replaced the TFI the 1st time I had already taken the hint to move the TFI off the distributor. I mounted it right up front in front of the radiator on the front support bar. I used a TFI heatsink that I pulled off a thunderbird, cleaned it completly with a wire wheel dremel tool and shaved off a bit here and there to make mine fit on it. I soldered all the wire connections also so I could be sure to eliminate wiring as a problem. I hacked up the known bad tfi so that I could run the 3 wires through it to the distributor and just mount it securly with the factory bolt holes. Used 2 part epoxy that says its good to 500+ degrees to hold the 3 wire connectors in the correct position of the hacked up tfi.


All the wires are carefully wrapped up with electrical tape untill I had time to get some wire covers.


I made sure I left enough extra length, but less than 12ft (wire lengths are recomended to be kept under 12ft because resistance), so that I could remount the whole assembly anywhere within the engine compartment if the location I chose did not workout.


The extra wire is neatly coiled up infront with the new tfi and out of the airflow for the radiator.


I think the 1st tfi I got as a replacement which fixed my no start problem was indeed somewhat defective because even with the new mounting location and heatsink still got very very hot. And yes I used the supplied silicone. O'Reilly's gave a lifetime warranty with that module so I returned it and got a new one just prior to making this thread. I told them the engine would stall every time when that module got to 160-180 degrees. They should it shouldn't even get that hot especially when the guy went out and looked at my new mounting location for it. The new one I got on there now (2nd one I've gotten but only paid for 1) does not even get the heatsink warm much less hot like the other one was doing. So I'm pretty sure I have got a good one now. I also used computer heatsink compund, the good stuff, that has 30% silver in it this time instead of the supplied silicone. I figured the only weak link in my new tfi setup was the compund so might as well go with the best this time and know its perfect. I have 8 syringes of it laying around anyways so it was basically free from my computer building days.

So tek, you think the thing that the tfi plugs into could be at fault? I've heard that you typically just replace them if they have the slightest hint of burn marks of are fading yellow. Mine looked bright white with no burns when I replaced the distributor cap trying to fix the no start problem, so I didn't bother with it. I guess its only $17.99 at autozone to be sure thats not my problem. Is it a quick replacement? From the picture of the module it looks like it would be a quick fix but looks can be deceiving.


When the pickup coil in my GMC truck was going out it caused a no run problem. The truck would start fine but then die within a second or 2. It would do that untill it got up to temperature (about 100 degrees or 20-30 cranks of the engine in 65+ degree weather) and then the truck would start and run fine unless it sat too long like at the grocery store. Having this problem for about a month untill I finally figured it out is what lead me to think the pickup in the Bronco was still good, as the Bronco does the exact opposite. It starts and runs fine untill it gets warm instead of not starting or running untill it gets warm.

[UndeadBronco]

Tek sir,

My Bronco has sat in the yard since your last post on this thread. I finally got around to replacing the distributor pickup about 2 weeks ago. I had just bought the plastic piece thinking it would just bolt or snap in there once the distributor was off but thats not the case at all.

Once you get the distributor off the engine then you have to push the pin out of the distributor gear. Then you have an appropriate size press (a big one) to press the shaft out of the distributor housing. Note, using a hammer and wood block to try and beat the shaft out will not work in any way shape or form (I tried). That will allow you to get the pickup coil off the housing. Next you put it all back on the shaft in the exact same position and press it all back together. I could have got out the anvil and the 10lb sledge and got the shaft out but there is no way I could have pressed it all back together that way while keeping all the little pieces in teh exact right positions. Basically you must buy a new/rebuilt distributor which is $60 + a $6 core charge if you don't have the old one with you.

Other bad things about replacing the pickup coil in the distributor is that you have to take the upper intake manifold off in order to get the distributor out of the engine. The intake is only 6 bolts 10mm size but there are tons of wires and other little things attached to it that must come off first. It comes down to about 2hrs of taking parts off and labeling or positioning them so that they can be put back on in a timely fashion. Then a run to the parts store with the old distributor to save the $6 core charge (they charge you tax on a core charge and its not refundable when you bring the old core in to get your $6 back) so thats 30 minutes. Then another 1hr - 3hrs depending on how well you decide to clean things while puting everything back on. So a 4-6 hr very messy job and having to extend yourself in very uncomfortable positions to get at the back of the engine where the distributor is not so conviently located. If one can find a mechanic that will shoot you a low quote on doing this job I'd say take it. If I were a mechanic I would deffinatly charge $200 or more + parts, and thats if I liked you.

With the new pickup in, the ol Bronco has worked almost perfect for the last 2 weeks. A little sputter here and there but its hardly noticeable. Then this past Saturday it just sputtered out and died at the 1st stop sign from my house. I was able to just put it in reverse and limp it back to the driveway but it sputtered and died 6 times doing this. It feels like a fuel problem unfortunatly. I know the in tank fuel pump is good because i can hear it running and its brand new. The one on the side rail is not nearly as loud. I have to have someone turn the key while I lay on the ground to be able to hear it kick on. My pump on the side rail is a salvage yard swap because I was suspicious of the original one that was on there. I decided to start by replacing both fuel filters since I had only replace 1 last year. The "canister filter" on the side rail I was not able to get it apart last year. So I went to the store and got teh right filter wrench this time and indeed got it apart. There was no filter in there just a long tube which would and indeed did prevent me from putting the right filter inside the canister. I tried it with the correct size filter, just kinda sitting in there but the O-ring leaked. So I took it apart again and tried it without the filter but it still leaked. So went to the salvage yard and cut one of these canister things off a bronco real fast to swap mine with. When shook, it is noticeable that there is a filter in tehre and it must not seal up very well or it wouldn't rattle around. So I did have the correct filter to go in there it just doesn't seal, which defeats the purpose of having a filter I would think since there is planety of room to bypass it. Well I swaped the salvaged one in and ol Bronco came to life again. Basically I didn't fix anything though.

When I couldn't get the canister to stop leaking I thought why not just remove it and connect the fuel lines together to eliminate that sill can. I second guessed myself though and thats how I ended up at the salvage yard. So I'd like to ask here, has anyone done this? I am sort of thinking that the can serves a purpose by keeping a small reserve of fuel up close to the high pressure fuel pump. So when/if you stomp on the gas the low pressure pump in the tank may not be able to keep up so theres that reserve close by to feed the High pump so the engine doesn't stall. I would really like to eliminate this canister because it is a major pain to take it apart and replace the filter or lack of filter in my originals case. Getting it back together without it leaking is also very difficult so thats another reason to eliminate it.

Also this business of 2 fuel pumps is a real pain in the ass. It makes no sense to have 2 because if the tank one dies the truck won't run or if the side rail one dies the truck won't run. 2 pumps just doubles the chance for something to go wrong. If one was just there as a backup then that would make sense! So I ask, has anyone fixed their Bronco with just one pump? If so how, or what pump would I use?

Any other suggestions on fixing or altering the Bronco fuel system or ignition system would be welcomed also as it seems in my almost 2 years of owning a Bronco its only weak points are are teh fuel & ignition systems. I would very much like to remedy this so I have another dependable vehicle.

[tekatlarge]

Hey undead,

Before someone says something, I might ask if you post asking for help or questions to please keep your posts on one thread. It is much easier for the person answering to have all the information in one thread instead of two or three.

I am not complaining mind you. I just find that when I post an answer or help someone it is easier for me to have all the information in one thread. That makes it easier to see what has been done what has been suggested and or what the problem is with details.

Now on this fuel pump and filters and two verses one pump give me a little bit and I will explain in easy to understand terms. I will get back to you by tomorrow, earlier if I get them damn
taxes done.

[UndeadBronco]

I thought about keeping the fuel system mod in this thread tek but I thought it shoud be a seperate thread since it is a mod rather than dealing with my no run problem. If any info was posted here on it I was going to transfer it over to the new thread as to keep things organized for someone that might want to do teh mod in the future.

So I went out and shot a vid of what this truck is doing so that it might be easier for all to undestand. It's up on megavideo and roughly 35 meg. I got down under the truck while it was runnign so that all could hear that both fuel pumps are working. The 1st time it dies you can distinctly hear the high pressure pump working. Because the muffler has a large hole/holes in it its hard to hear the in low pressure pump working int he tank but I assure you I can hear it working fine. Note that the fuel gauge does not work but I just put in 7 gal of fresh gas from my gas cans so it's not empty.
http://www.megavideo.com/?d=B9OTQ3G1

As you can see the truck starts up every time without a problem but after a few minutes it will stuble out and die. Here's a list of everything that has been done in the order it was done so that everyone can stay up to date.
Battery
Spark Plugs
Plug Wires
Distributor Cap & Rotor
Ignition Coil
Replace all cables that lead to or from the Battery or Grounds
Oil & Filter
Fule pump in the gas tank
Inline Fuel Filter
Fuel Pressure Regulator
TFI Module
- The truck ran for a week after this then started dieing again.
2 months later rewired a new TFI to the front of the truck on a heatsink so it stays cool
- The truck ran for a week after this then started dieing again.
Fuel Pump on the frame was replaced with a used pump from the salvage yard.
Distributor Assembly (Complete housing with shaft, gear, and pickup coil)
- Worked flawless for 2 weeks and now dies as you see in the video.
Changed both fuel filters on the side rail

[Ranger Dave]

This video is unavailable.

[UndeadBronco]

Sorry RD apparently megavideo changes the file path/url once they have approved a video for public sharing. Post has been edited with correct link.

[Ranger Dave]

you have a spare computer?? try one from a 88+. or try disconnecting the vac. line to the EGR

[tekatlarge]

I am with Dave after watching the video. While the engine is idling pull and plug the vacuum line from the EGR valve. Also if you can swap the ECU I might do that. This is reminding me of something I have seen before but I just can't remember what it was.

Does the engine die only when idling or if you ran it say at 2000 and held the rpm constant will it die out then. If it only dies out at an idle and the EGR doesn't make it run bad then you need to look deeper like maybe the IAC. Idle air controller. I got something round here on that bugger and I will try to drag it to life in the next day or so.

I am not so inclined to blame this problem on fuel delivery but possibly oxygen sensor or IAC. I also have to ask if you have run the computer for codes? If you need help I have a document on my site that shows you how to run koeo tests and other diagnostics. just look for B II diagnostics there.

OK now back to work and keep us informed to your findings.

[Ranger Dave]

i had the same thing happen to my 86 ranger. i changed everything,didnt help.i put a 89 computer in it, all better. and if it put the 86/87 computer back in,runs like shit.

[UndeadBronco]

Sorry for the delay I had to work on Friday and Saturday.

This morning I undid the EGR and that didn't help anything or change it at all. I 1st just pulled the green tube off the EGR (the one that goes to a type of pressure switch next to the starter relay), no change. So I reconnected the green tube and pulled the tube that goes to black box mounted above it on the upper intake manifold, no change. Next I tried unpluging that black box and still no change. Lastly I undid both tubes and the electrical connector to the black box and still no change.

I had cleaned the EGR and the IAC last year when I was dealing with the no run problem which turned out to be the TFI. The IAC only comes apart so far though so. I also remember putting on a spare IAC to test if it was a problem.

After messing with the EGR and no luck I swaped out the computer since I had a spare from my work on the truck last year. I remounted the computers ground this time just to be sure but still no change.

It sputters and dies if I just let it idle. If I throttle the pedal I can get it to stay running for a about a minute or 2 longer but it will still eventaully sputter out and die.

Theres an electrical box with vac line ran to it, which is mounted on the firewall just to the left of the upper intake. I can't recall the name of the box but it starts with an S. I remember reading how important they are but I think that was only for getting the engine started not while running.

I'm really lost on this one. Its got to be something that changes when the computer sets the truck into RUN mode after starting though. A couple control are essentially bypassed when 1st starting a car with EFI and then it goes into RUN mode after 5-10 seconds typically. Thats why idle drops after a few seconds when 1st starting a car. I'm not sure what the variables are that tell the computer to go into RUN mode though.

[Ranger Dave]

you said you changed the computer, ta what year

[tekatlarge]

Have you hooked up a fuel pressure gauge and watched the pressure when it is running and then when it is dying? What is your pressure readings?