77 dies random when warm

hello,  I have a 77 bronco with 302 and hei. When im driving around it will die at random after it gets warmed up, sometime I can drive it 5 miles and sometimes 20 but I happens every time I drive it. I replaced the module and put it a cooler spot, last time I drove it the module wasn't hot at all when it died. I also replaced the battery which actually seemed like it helped but might have just been luck. I also replaced the fuel filter, it wasn't dirty but I replaced it anyways, I replaced the detached solenoid. When it dies, sometimes it will start and I can make it home if im close, but it usually dies a few times and wont start back up for a good while. I also feel like my battery is not charging good, but that might be because I don't drive much. thanks in advanced. I did a search and found a few ideals but still need some advice

Hey Justin, Welcome.

When your truck dies, and won't restart I assume that it will crank, but the engine will not fire...correct?

If that is the case, check to see if you have spark.

No spark is usually a module, but you said you replaced that. The other possibilities are:

1- the pick up coil in the dist.

2- the coil itself

3- wiring to the primary side of the distributor.

Get a test light and carry it with you when you drive.  when the truck dies, connect the test light between the + and the - side of the coil. Crank the engine and see if the light flashes.  If it flashes the coil is getting a "fire" signal and the primary side of the ignition system is ok. The problem could be the coil is not firing, ( needs replaced), BUT be sure the problem is that your are not getting spark.

Another possibility that I have found is the fuel pump relay overheats and opens the circuit killing the fuel pump.

If you have spark, you may not have fuel and the reason could be the relay.  You should check the circuit. Sorry I do not have a diagram to place here. I'm sure M5 or one of the other guys that have more resources could get you one.

Bottom line check for spark...and fuel....not likely your battery is the problem unless the truck won't crank.

Let us know how things turn out.

Ok thanks for your help. I will give those things a try

yo justincat

WELCOME!

Do you have the MSD6AL module? See their troubleshooting docs @ http://www.msdperformance.com/product.aspx?id=16013

Excerpts;

"CAPACITIVE DISCHARGE

The Digital 6A and 6AL feature a capacitive discharge ignition design. The majority of stock ignition

systems are inductive ignitions. In an inductive ignition, the coil must store and step up the voltage

to maximum strength in between each firing. At higher rpm, since there is less time to charge the coil

to full capacity, the voltage falls short of reaching maximum energy which results in a loss of power

or top end miss.

The MSD Ignition features a capacitor which is quickly charged with 520 - 535 volts and stores it until

the ignition is triggered. With the CD design, the voltage sent to the coil positive terminal is always

at full power even at high rpm.

Experience at the races has shown that if your engine is experiencing a miss or hesitation at higher

rpm, it is usually not directly ignition. Most probable causes include faulty wiring, a coil or plug wire

failure, arcing from the cap or boot plug to ground or spark ionization inside the cap. Several items

to inspect are:

• Always inspect the plug wires at the cap and at the plug for a tight connection and visually inspect

for cuts, abrasions or burns.

• Inspect the Primary Coil Wire connections. Because the MSD is a Capacitive Discharge ignition and it

receives a direct 12 volt source from the battery, there will not be any voltage at the Coil Positive (+)

terminal even with the key turned On. During cranking or while the engine is running, very high voltage

will be present and no test equipment should be connected

the connections are clean and tight. If you are not

running an alternator this is an imperative check.

If the battery voltage falls below 9 volts during a

race, the MSD output voltage will drop and the

current draw will increase.

• Is the engine running lean? Inspect the spark

plugs and complete fuel system.

• Inspect all wiring connections for corrosion

or damage. Remember to always use proper

connections followed by soldering and seal the

connections completely.

If everything checks positive, use the following

procedure to test the ignition for spark. MSD also

offers an Ignition Tester, PN 8998 or PN 8996. This tool

allows you to check your complete ignition system

while it is in the car as well as the operation of rpm

limits, activated switches and shift lights.

CHECKING FOR SPARK

If triggering the ignition with the White wire:

1. Make sure the ignition switch is in the “Off” position.

2. Remove the coil wire from the distributor cap and

set the terminal approximately 1/2" from ground.

3. Disconnect the MSD White trigger wire from the distributor.

4. Turn the ignition to the On position. Do not crank the engine.

5. Tap the White wire to ground several times. Each time you pull the wire from ground, a spark should

jump from the coil wire to ground. If spark is present, the ignition is working properly. If there is no

spark skip to step 6

----------

How to Troubleshoot a 1977 Ford Duraspark 2 Ignition System http://www.bobcat.ca/stuff/DOCS/DURATR~1.PDF

How to Troubleshoot a 1977 Ford Duraspark 2 Ignition System http://diagnosecarproblems.blogspot.com/2009/12/how-to-troubleshoot-1977-ford-duraspark.html

ok, I will probly get a chance to drive it 2morrow and test it out. Ill just drive around the house and see if its spark or fuel related. Its not a msd, I believe it is a motorcraft module from autozone. It makes sence it something  electrical  or fuel relay because it runs just perfect and then just shuts down, it don't ever hesitate or miss or anything like that, it runs perfet, or not at all. I will also pull a plug and see if its been running lean. thanks again,

You won't have a "relay" on your fuel system.., unless someone put on an aftermarket elect. fuel pump way back when.

The '77 year model did come with Motocraft elect. ignition. (Duraspark)

There were some issues.., usually the coil or pick-up coil as stated above.

Should it be the pick-up coil.., get one fr. Ford or Napa.

There's a "tiny" drift-pin holding the armature in place. Be careful NOT to lose it. I layed some little magnets 

in there to catch it when I pulled mine.

I bought a pick-up coil fr. O'reileys Auto.  It was too big & the armature rubbed on it making a strange noise. <_<

I put the original back in & it's working fine.

Good catch on the fuel relay Bob....I'm constantly thinking EFI.  I should pay more attention to the year.

No biggie.., we never really know what eng. is in these rigs until the owners offer up that info.

well, I still haven't had a chance to get someone to ride with me yet to test it. I might just go to napa  2morrow and get the coil so I can try it without another person. Is the pick up coil in the coil,  or is the coil and the pickup coil 2 different things? thanks

An ignition coil is not that expensive sooooo,  trying a new one is a good test.

The pick-up coil is inside the distributor..., it takes the place of points.

If the coil doesn't solve it.., come back & we'll go over the pick-up coil.

10-4.

What about vapor lock in the fuel system?  

Good point Genthree..,I just assumed Justin checked the fuel issues.  Even a bad/failing fuel pump could 

raise havoc.

As to Duraspark..,

http://www.ford-trucks.com/forums/1157851-a-troubleshooting-tip-for-those-with-duraspark-ignition.html

----click the above---

And, a new coil should be compatable with Duraspark ignition.

P.S.  I believe the '77 EB had Duraspark II  (check me on this)

Sounds more like the pickup inside the distributor to me.

Ya.., good possibility..!

When mine died, it was the main coil.

I ended up puting the original pick-up coil back in as well.

Both the pick-up & the main coil are testable (ohms)  if one finds the specs.

Hey guys, maybe the same issue. Just bought a 74 bronco at the beginning of the year. It has stalled on me 3 1/2 times now, all while accelerating. The first 2 times I blamed myself as I thought it ran out of gas. (Fuel gauge doesn't work and new to dual tanks). Last night, it happened again. This time I know both tanks are full as I just filled them the night before. All three times, the only way to start it is by pouring gas into the carb. 1st time, accelerating from stop sign and it cut out silently(no choking, stuttering, didn't even know I was without power). 2nd time, accelerating from 50->55. Gave it gas and felt like it flooded, instant no power. Admittingly, I adjusted air/fuel mixture screws as I was getting a strong gas smell prior). 3rd time, was the next day. Accelerating after a turn. Stuttered a bit like it wanted to keep going, but coasted to the side. This time, it reluctantly started without gas, but did the exact same thing around a turn 1/2 mile down the road. The only way to start was by adding gas to carb. Any thoughts? I really want to get the opportunity to drive my bronco. Thanks

Worst case.., there is always a chance there's two issues rearing their ugly heads..! (fuel & electric)

Your post sounds like fuel. Have you tested the accelerator pump by manually (key off) moving the throttle

while look'n down the carb. throat..?  Should see the nozzle(s) squirt. 

Is the carb a stock 2 barrel.. .?

Dirty jets, durty needle-n-seat, or a sticky float, and a worn out accel. pump could be causing this.

When it quits, it's easy to check for spark via a spark plug wire.

Pouring in fuel (& it starts) leans more toward a carb issue.

Hi Bob. Thanks for the suggestions. Holley 4 barrel. When it is running, yes, all jets are squirting. When it stalls, nothing. So I thing something is causing it to starve. Vapor lock? I am Chicago and it is 30 degrees. I followed my fuel lines and nothing is direct on the engine block. But after many emails, may have found my problem. Although my bronco is a 74, I don't see any ventilation in the tanks/fuel line, and my gas cap is not vented. I just drilled a hole in my cap to see if that does the trick. If this works, I'll go out and buy some vented caps. If it doesn't, I'll check fuel filters and see if there is something sloshing around inside that is clogging the filter?

There's also a strainer on the pick-up tube in the tank(s).  Debris can float around & stick to the pick-up screen, 

Then release when the suction stops.

Ya, vapor lock isn't likely.