'78 351m dies at idle - FSB Forums
 
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post #1 of 10 (permalink) Old 06-17-2009, 03:27 PM Thread Starter
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'78 351m dies at idle

First - I used search and didn't quite find an answer to my problem on the forum. The answer could have been there - but when it comes to the mechanics of an engine I need a pretty dumbed down answer.

Ok - my bronco drives great. No issues with it dying when I am moving. The only time I have problems is when I am stopped for an extended period of time, typically during hot weather conditions (think drive through, long stop light, waiting to get past the security checkpoint to get on Fort Leonard Wood...).

I am able to keep it running by revving the engine - but of course I'd rather not have to do this.

Any advice would be wonderful.



Also - searching this forum made me think it would be either very difficult or very expensive to change the rear main seal in my bronco...I think the other junior bronco home mechanics should know that with a lifted 78 bronco - it is a pretty quick and simple job to replace the seal - not need to jack it up or remove anything other than the oil pan and main bearing...
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post #2 of 10 (permalink) Old 06-17-2009, 03:36 PM
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Originally Posted by DEFLjon View Post
Ok - my bronco drives great. No issues with it dying when I am moving. The only time I have problems is when I am stopped for an extended period of time, typically during hot weather conditions (think drive through, long stop light, waiting to get past the security checkpoint to get on Fort Leonard Wood...).
Think insufficient cooling.

Insure you have a good water temp gauge so you can eliminate that as a cause.

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if you still can't figure it out put it back together and take it to a mechanic
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Truck was stolen & sold for parts Wheat Ridge Colo Black with Red 2 tone. About $20K in the truck. VIN U15HLEC0170
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post #3 of 10 (permalink) Old 06-17-2009, 04:44 PM
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Maybe turn the idle screws up on your carb? whats it idle at before it dies? Id set it to about 700 rpm hot idling
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post #4 of 10 (permalink) Old 06-17-2009, 05:02 PM
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Think insufficient cooling.

Insure you have a good water temp gauge so you can eliminate that as a cause.
This is a new one to me, so your telling him it's seizing up and dying???

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Originally Posted by 7bronco8 View Post
Maybe turn the idle screws up on your carb? whats it idle at before it dies? Id set it to about 700 rpm hot idling
The first thing you do is inspect allvacuum lines, vacuum leaks are great for no idle, once choke is off, oh make sure choke is coming off, should be if your not having any other driveability problems, double check timing, check usual tune up items (ie plugs, wires, cap rotor), is it missing(shaking)?, The last thing you should do is start messing with the carb, especially if your unfamaliar with them, these are very simple carbs but, can be screwed up big time by the inexperienced.

J.M.
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'75 Fiat 124 Sport Spider 1800/5spd
'75 Fiat 131S 2dr
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post #5 of 10 (permalink) Old 06-17-2009, 05:52 PM
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Bronco Info: 1978 ford bronco. 351m np435 np205 3in of lift. 35" radial mud rovers.
dont forget to check the ignition control module, that started makeing mine run funny.
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post #6 of 10 (permalink) Old 06-17-2009, 06:45 PM
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Think insufficient cooling.

Insure you have a good water temp gauge so you can eliminate that as a cause.
I could be wrong but don't think he mentioned anything about it getting hot
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post #7 of 10 (permalink) Old 06-17-2009, 07:23 PM
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Quote:
Originally Posted by colobronco View Post
Think insufficient cooling.

Insure you have a good water temp gauge so you can eliminate that as a cause.
your probably on to something here.


at idle if the clutch fan is wasted the engine will start to over heat. ya, it might only hit 220-240, but with the under hood temps going higher than that you could very well be witnessing vapor lock.

your under hood temps are boiling the fuel in the fuel line to the carb and not allowing the pump to supply fuel to the carb at idle.


but what the general total running state of the truck?

last tune up?
last complete filter change?
engine idle?
auto or manual?

'01 F250, 444ci of straight piped oil burning fun. 4x4, 6 spd, GTP38R noise maker, Stage 2 injektorz. Lotsa fun!


Let's Go Fishing.
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post #8 of 10 (permalink) Old 06-17-2009, 09:28 PM Thread Starter
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I'll check the vacuum lines later tonight. As far as the plugs, wires and rotor cap - they are all still fairly new. The only filters I've changed thus far are the oil and air filters.

Other than this issue the engine is running well, as far as I know. I do not have a tachometer and my oil/temp guages are not working, but after I fire it up, it does drop to a decent sounding idle. The bronco is an automatic.

Like I said before it drives great until I get stuck in a line on a hot day. After it has died once (the taco bell employees were kind enough to give me a push out of their line) and it took about 45 minutes to restart it - it is hard to say if it took this long to cool down or if I flooded it trying to restart early on.
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post #9 of 10 (permalink) Old 06-17-2009, 09:53 PM
Im scared of jopes
 
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First thing you should do is go pick up some mechanical oil and temp pressure gauges, 2 main things man. Then go from there, Be more specific, It took 45 minutes to start? Like it would just turn over and over till it cooled down? Battery didn't have enough juice to crank it anymore?

EDIT: sorry read more, It did crank. Fuel filter or pump?
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post #10 of 10 (permalink) Old 06-21-2009, 08:21 PM Thread Starter
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I am leaning more towards it being a temperature issue. My upper radiator hose is beginning to bulge on the radiator end...could there be some sort of blockage in the thermostat that would cause this? It is also starting to drip from the engine end of that hose. The clamps are secure themselves, the hose is not loose.

It seems my oil is burning at an increasingly rapid rate. It is leaking very little since the change in rear main seals, but I am having to add oil just as frequently now.

I purchased a mech temp & oil pressure gauge that will arrive on tuesday, this will confirm how hot it is running.

I am new to engines with a carb - so I am not sure if this could be related, but I put a new gasket on the base of the carb and in reinstalling I broke the choke tube running to the manifold. I fabricated my own...could a deficiency here cause my problem? Also, the white sleeve that I put over the tube is beginning to brown (thing the color of a nicely roasted marshmallow)...again, a heat related issue.
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