Hot start problem - Ford Bronco Forum
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post #1 of 21 (permalink) Old 03-16-2017, 01:36 PM Thread Starter
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Hot start problem

I have a 96 Bronco with 5.8 When cold, it starts and runs great. After reaching normal operating temperature, it still runs great until I shut it off and let it sit for a bit. Like going into a store. Then trying to restart, it acts like it is trying to run on a couple of cylinders. Sometimes after chucking along in this state for 10 seconds or so it will either die or catch and run normal. If it catches, it runs great again. If it dies, usually it will not start again until the engine has set and cooled for about half hour. No codes are being set. I've replaced all ignition parts, and after some internet searches, the fuel pressure regulator.

Thanks for any help.
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post #2 of 21 (permalink) Old 03-16-2017, 02:31 PM
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Yo Mav,
Long Crank Times may be traced to a sticking Idle Air Control (IAC) valve, TSB 97-9-5 for 95-96; "...After a 1-4 hour engine soak time, long crank times and/or long crank to start followed by a stall may occur on some vehicles. No further stalling or rough idle will occur after the engine is running. The long crank and/or stall may be due to the Idle Air Control (IAC) Valve sticking. Replace the IAC Valve with a revised IAC Valve if no Diagnostic Trouble Codes (DTCs) are present." @ http://www.stangnet.com/images/stori...s/97-09-05.pdf
I did it once for our 96, but also need to clean IAC passage and maybe intake manifold.

"If the engine RPM does not drop when the IAC motor is disconnected, then either the IAC motor is not functioning properly, or, there is a vacuum leak in the engine. Stop the engine, remove the IAC motor and block off the passages. Restart the engine to see if there is any change in engine RPM. An idle speed higher than base idle specs indicates a vacuum leak. If the engine RPM is at base idle specs, then the IAC motor is bad. Resistance specs are 7-13 ohms. A good resistance reading does not necessarily mean that the IAC motor is good. Occasionally, an IAC motor will become weak, and will actually bypass too much air, causing a high idle condition even though everything else is operating properly..."
Source: by Mike N via Joe D

IAC Overview, Cleaning & Testing (testing is different than above article) by Ryan M @ Fuel Injection Technical Library Idle Air Bypass (IAB)

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post #3 of 21 (permalink) Old 03-17-2017, 07:57 AM
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I have a similar issue. When my '95 5.8 is at normal operating temp and I stop for gas or run into the parts store, it rolls over real slow and then it will catch and fire up. I have checked the battery and its good. I have replaced the cables with a larger gauge version and cleaned all the connections but it still cranks slowly a few times when hot than it always starts up????
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post #4 of 21 (permalink) Old 03-17-2017, 09:44 AM
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Yo apachesix,
It's better to establish your own thread so that old fools like me don't confuse yiu6r issue with original poster's.
Did you check cables and connections at starter solenoid atop starter too?

Sone possible causes of Starter Motor Cranks Slowly:
Loose or corroded battery cable connections.
Undercharged battery.
Loose or corroded starter motor connections.
Malfunctioning starter motor. Perform starter load test; pull starter and have it tested at suitable shop that has capability to test, including the;
" Voltage Drop Tests; If the starter cranks slowly and the battery is satisfactory, there may be a malfunction of the starter or in the cranking circuit wiring. To determine if the problem is in the wiring, a voltage drop test must be performed on the following:
motor feed circuit
motor ground circuit
individual cables
These tests are performed to determine if there is excessive resistance in the starter motor circuit. Always make the volt-ohmmeter connections at the component terminal rather than at the cable wiring end connector. Making a connection at the wiring end connector could result in false readings because the meter will not pick up a high resistance between the wiring connector and the component."
...
Individual Cable:
A battery cable problem can produce symptoms similar to a dead battery, bad solenoid, or weak starting motor. If the cables do not allow enough current flow, the starter will turn slowly or not at all.
Connect positive (+) lead of Rotunda 73 Digital Multimeter 105-R0051 or equivalent to battery positive (+) post. Connect negative (-) lead to starter solenoid B terminal. note that this the solenoid mounted atop starter.

To locate excessive voltage drop in cable, move multimeter negative (-) lead toward battery and check each mechanical connection point. When high reading disappears, last mechanical connection point that was checked is the problem." by Ford

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post #5 of 21 (permalink) Old 03-17-2017, 05:11 PM Thread Starter
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Thanks for the response. I replaced the IAC today but unfortunately it did not fix the problem.
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post #6 of 21 (permalink) Old 03-17-2017, 07:22 PM
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Yo Mav,
Was there much gunk in the passageway?
Inspect the throttle body. Check for objects blocking the IAC passage or throttle bore. Excessive deposits, especially on high-mileage engines, can build up in the IAC passage and on the IAC pintle. Excessive deposits can also build up on the throttle plate, so check for a sticking throttle plate.

Check the passages for carbon build up. If they are plugged they need to be cleaned out.
How to Clean and Test your IAC

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post #7 of 21 (permalink) Old 03-17-2017, 11:31 PM
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Quote:
Originally Posted by Mavaholic View Post
Thanks for the response. I replaced the IAC today but unfortunately it did not fix the problem.
What brand? I replaced mine with a NAPA unit and observed no improvement. Put in a Motorcraft unit and most of my problem was solved.
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post #8 of 21 (permalink) Old 03-18-2017, 06:46 AM
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sorry, I thought maybe there were some similarities. Thanks for the help.
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post #9 of 21 (permalink) Old 03-18-2017, 09:52 AM
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Quote:
Originally Posted by forbye View Post
What brand? I replaced mine with a NAPA unit and observed no improvement. Put in a Motorcraft unit and most of my problem was solved.
Yo forbye, mind if I add your experience to the Defective Parts Listing ?

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Last edited by miesk5; 03-18-2017 at 10:02 AM.
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post #10 of 21 (permalink) Old 03-18-2017, 10:24 AM
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Yo Guys,
Test what you have;
How to Clean and Test your IAC


apachesix, Try a Self Test for Diagnostic Trouble Codes ( DTC ) s by my pal , BroncoJoe19

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post #11 of 21 (permalink) Old 03-19-2017, 01:00 AM
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Yo forbye, mind if I add your experience to the Defective Parts Listing ?
Please do. I had forgotten about that list.
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post #12 of 21 (permalink) Old 03-19-2017, 09:11 AM
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Quote:
Originally Posted by forbye View Post
Please do. I had forgotten about that list.
Yo,
THANKS!
DONE @ Defective Parts Listing

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post #13 of 21 (permalink) Old 03-19-2017, 10:00 PM
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Have you tried to test anything at all WHILE it is acting like this?

If you are looking for a silver bullet fix here it is- Do NOT listen to a bunch of apes on the internet telling you to buy xxx or buy yyy without even being there to see it or going off ZERO test results. If you can not find something DEFINITIVE while the truck is running poorly, DO NOT waste your time and money on guesses, go to a reputable mechanic in your area and he will save you lots of guesswork and heartache.

"Oh man, lodged where??"
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post #14 of 21 (permalink) Old 03-20-2017, 12:21 PM
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check the fuel pressure mine has the same issue. I don't have a fix but it loses pressure as soon as the key is off.
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post #15 of 21 (permalink) Old 03-20-2017, 01:34 PM
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This happened to me. Turns out the negative battery cable's insulation was worn and touching the engine block. Heat will cause electrical resistance so make sure your battery and starter cables are in good condition and not touching the block.

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post #16 of 21 (permalink) Old 03-23-2017, 12:27 PM Thread Starter
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OK Finally got time to work on it again. Bought a fuel pressure gauge and found when cold, key on, engine off, pressure was only 15lbs. Once started, jumped up to 30. After warm up and trying a hot start, pressure was down to around 8psi. So I'll try the filter first although I removed it and can blow through it with ease, I'll go ahead and replace it. Looks to be the original one. Then on to the pump. Next question is there an access panel in the floor or do you have to drop the tank?
As far as taking it to a qualified mechanic, I'm the only one I can afford. I've worked on cars all my life, just never messed with anything newer than 79. So fuel injection is a learning experience. Even if it is a pump, my total investment will be less than $400. I doubt the mechanics bill would be that low so its worth it to me.
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post #17 of 21 (permalink) Old 03-23-2017, 01:12 PM Thread Starter
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A little more internet research and I see there is no access panel. Dropping the tank wouldn't be a huge deal other than it has a full tank of gas and up until a few years ago it spent all its life up north. So its pretty rusty underneath. Most of the bolts will probably have to be cut off. As far as emptying the tank, anyone see a problem with disconnecting the line off the input of the fuel filter, stick the end in a container, turn the key on, and using the tank pump to pump it dry?
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post #18 of 21 (permalink) Old 03-23-2017, 02:53 PM
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If you cut the access panel you don't have to drain the tank. I cut my access panel with air nibblers, as I was concerned that any other method could cut the lines (fuel supply and return) or the wiring. Power shears would probably work too.

http://www.supermotors.net/registry/media/1026068

(The previous/next pictures at Supermotors have a few more views of my access panel)

A die grinder has the potential to be dangerous in that cutting a fuel line would be spectacular, but would probably result in more problems than just a replacement fuel pump. There was a member here that took a garden hose with a fine spray and sprayed the underside of the bed and the top of the tank while he used a grinder to cut the hole.
Read this for more information on cutting an access panel.
1983 Ford Bronco Bronco Fuel Pump Access Hole pictures, videos, and sounds | SuperMotors.net

"The simplest solution is usually the best solution" - Occam's Razor

"The significant problems we face cannot be solved at the same level of thinking we were at when we created them." - Albert Einstein
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post #19 of 21 (permalink) Old 03-23-2017, 03:16 PM Thread Starter
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I have given serious thought to cutting an access panel. However, the tank and tank guard have so much heavy rust that I'm thinking of dropping the tank anyway just to clean it all up and get a good coat of epoxy paint on everything. I may find out rust is the only thing holding the gas in. I'm living in FL now so road salt will never touch it again.
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post #20 of 21 (permalink) Old 03-24-2017, 07:35 PM Thread Starter
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Dropped the tank today. Was a pain because of it being almost full and the rust. Most of the bolts had to be cut off . Once the tank was out, the Locking ring and tabs just crumbled away so a new tank is in order. Also the rear frame mount and back mounting area on the skid guard is swiss cheese so I have some fabricating to do.
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