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Code 53 from Continuous Memory indicates the TPS output voltage has intermittently been above the maximum ~4.5 VDC when the engine was running. It is a historical code from days, years, decades ago. KOEO Code 53 indicates the TPS is currently above 4.5 VDC. The computer will shut off the injectors while cranking the engine if the TPS output is above ~4.0 VDC perhaps a bit more. This is a function to allow the user to clear a fuel flooded engine. A quick test is pull the connector to the TPS then try to start the engine.
 

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Yo Millie,
89 Bronco Grounds from 89 EVTM:
Including at passenger side Frame;
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Rectangle Font Material property Screenshot Parallel

Here are some PCM KILLER perpetrators and other causes:
Smell around the PCM. If it smells like dead fish, it's bad.
Look for PCM printed circuit board burn marks around leaking capacitors, resistors.
View attachment 182797
For example, see Old leaky capacitors in swapped EEC and no more codes by jowens1126
Water damage from cowl leaks, ESPECIALLY if you you have wet carpet or mat near driver kick panel; or on PCM Connector due to a bad hood seal near cowl panel, viewable with hood up.
Corrosion or damage due to moisture is one of the main reasons for failure. Corrosion can enter through the wiring harness and moisture can enter by a failure in the seals in the PCM itself. This happens over a period of time (5 to 10 years) due to exposure to the elements.
The alternator could be generating an AC voltage spike due to bad diode(s) or supply Voltage
View attachment 182796
Overloads.
I recommend bench-testing the alternator for voltage output and AC voltage ripple.
Thermal stress due to excessive heat and excessive vibration that causes sensitive parts to fail.
Bronco was jump started on reverse polarity.
Connector pin damage or corrosion,
Other internals:
broken tracks,
cold solder joints,
short circuit,
thermal stress due to excessive heat and excessive vibration that causes sensitive parts to fail,
Overheated PC,.
Bad Intel 8061 chip or bad Intel 8361 memory chip,
Bad Internal Voltage Regulator, see Wayback Machine by absent member Fireguy50 (Ryan M)
 

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Discussion Starter · #23 ·
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Here is an image of the board, I looked at the other threads with burned/corroded sections but this one looks really clean. I had a flashlight under it to check for breaks as well.
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I will get started on the other suggested checks here shortly
 

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Here are some pictures of leaking capacitors inside a EEC

 

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Discussion Starter · #25 ·
I don't see anything that looks like it's leaking and it looks like all the little legs on the capacitors are intact. I also got a second set of eyes on it (he does computer board repairs on the side) and he said it looked to be in good condition. I'll do the bench test on the alternator, pin out the TFI, check/clean the rest of the grounds on the list, and try to start with TP sensor disconnected. Also planning on checking the rest of those fuse links with a test light once I figure out how to do that. Also thought I would detail the bay as I go and replace the wire sleeves.

The engine bay is going to end up being the cleanest part of this truck, I still have a long way to go on the exterior 😅
 

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I had a similar issue with a crank no start and it turned out to be the pick up sensor inside the distributor. I replaced the distributor (my first time ever) rather than trying to take it apart (It was not a Motorcraft). Fired right up.
 

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Discussion Starter · #27 ·
Is there a cold start injector or something similar controlled by the coolant temp sensor?
 

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There is no cold start injector or anything similar to that on these trucks. The computer will increase the injector on time to increase the amount of fuel based on various sensors including the ECT and Air Charge Temperature (ACT). Consider this extra fuel the equivalent of the "choke" system on a carb.equipped engine. Instead of limiting air the computer increases fuel.
 

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I'll repeat myself, because you didn't comment on it.

There are three grounds on the upper radiator support. One on one side, and two on the other. Meaning left hand side, and right hand side. You mentioned that you only checked ONE ground on the radiator.
 

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Discussion Starter · #30 ·
I cleaned the other grounds by the radiator and another one I found on the firewall, I also checked everything I cleaned for resistance from the negative terminal and they look good. I float charged the battery while doing that and ran to get some more gas to make sure it wasn't too low to start. It was at 1/4 so I put in about 5 gallons. I put the computer back in and tried to start. Still cranking but nothing, but I have no pressure at the rail anymore. The fuel guage on the dash read that I maxed it out then when I turned key to on it went down to half then back to max, I cycled it on and off maybe 6 times and now it's steady at 1/2 but still nothing at the rail.
I also tried to start with TP sensor disconnected but ended up with a koeo code 63 throttle position sensor circuit out of range (low)
 

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Discussion Starter · #31 ·
I tried to start again after I plugged in the TP sensor and she fired for just a second then died but still no pressure at the rail. I made sure everything was plugged back in and checked I didn't accidentally knock the intertia switch
 

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Oh boy, I don't want to lead you down the wrong road, so try to get a second one to comment on this.

I believe that when the gas gauge goes all the way to pinned at max it is shorted to ground. With that thought, you might want to crawl under the truck and look at the wiring to the rear pump. Maybe it somehow got pinched when putting the tank back in.? Maybe?
 

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Yo Joe & Millie,
Test gauge resistance as shown in "Incorrect gauge readings"; "check sender resistance"
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Discussion Starter · #34 ·
I cut an access panel so checking those wires shouldn't be so bad, but maybe I cut something? I was following wires underneath yesterday and found a ground strap from frame to body that I do need to replace but nothing else obvious. I'll take another look and check what's on the chart.
 

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I cut an access panel so checking those wires shouldn't be so bad, but maybe I cut something? I was following wires underneath yesterday and found a ground strap from frame to body that I do need to replace but nothing else obvious. I'll take another look and check what's on the chart.
Yo millie,
Good!
Also, Tech Tip Guide, General; "...Many times, the Ford fuel pump hanger/sender assemblies are frequently found with extensive corrosion on the cover and on the metal tubes. Over time, the terminals can loosen and cause intermittent loss of continuity. Erratic reading of the fuel sender level is one of the other problems that could occur..." by spectrapremium.com
 

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Discussion Starter · #36 ·
Hello, so I checked the old an new sending unit and noticed 2 things (new one is installed, old is pulled out on the table) resistance readings for old one are difficult to get because of corrosion, it's random 20-140 when empty and if I lift the float it stops reading. On the new one it's a steady 4. However problem #2 is that between the two units it's giving me a reading from different pins?


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Discussion Starter · #37 ·
I also checked with a test light for the ground from pin to pigtail and the light does come on for the pin that the two sending units are heading in common. It is a faint light though
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Yo,
For now, I need to do work:
Go by wire colors at the fiel gauge Sender connector.
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Discussion Starter · #39 ·
I did some more tests. If I ground the guage wire it reads empty, if I remove ground it goes back to max so I think the guage and wires are good. I plugged in the old sending unit and moved the float manually and got a good follow along with the guage as long as I put tension on the float rod for good contact.
Re-did the ohms check on the new sending unit and got a 70 for resistance on correct terminal (I wasn't making good contact when I tried before)
I also checked the ground on the negative side of the in line pump and that's good. I checked more fuse able links by the battery that went to a yellow wire like the diagram suggested and they all have continuity.
I pulled the relay for the EEC and fuel pump and checked resistance there, EEC had 80 and the fuel pump relay had 60. Could the lower resistance reading in the relay cause an issue?
I think this issue may be beyond me at this point but I can't find a mechanic nearby that will work on 89 electrical. I was really hoping I could get the bronco running because I'm trying to save money for my excursion so I can have the engine rebuilt. 😔
 

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The picture in this tread is mine.

If you jumper from the fuel pump test pin, to the signal return ground, your pumps should come on. If they don't, then run a wire from the fuel pump test pin the your battery neg terminal. Again they should come on. If they don't then check for power at the inertia safety switch (with the key ON and the jumper set.)
essentially you have to track down, the flow of power, from the battery to the relays, to the inertia switch, to the pumps.
 
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