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New Owner of a 720 (with many problems)


Brandon.fair

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So I added some tech-ron to the tank when I filled up today and on the way home I noticed that the "sputtering issue" would start at 3500 rpm. Where is previously started at 3000. So I thought it was working. But now it won't idle again. Has anyone experience this after adding fuel treatment? I'm having surgery tomorrow and my friend is taking me. But he won't be in town for a while and I'll have no way of getting around if I don't get this fixed. Any help is appreciated l.

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Probably not your idle issue but will definitely starve your carb at higher rpm's under load "driving". That was a lot of Crap in your carb, you want to make sure it is getting clean fuel. You have an electric pump. Change the filter, disconnect the fuel line from the carb and place it in a bottle and turn ignition to on the flush the line. Check the gas for crap. You may be cleaning the carb only to be pumping crap back in.

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Changed the fuel filter and hoses. Still won't idle. It will idle if choke is closed so I'm thinking it's to lean for some reason. Float level is at the dot. I just sprayed out the Jets. Fuel filter at banjo is clean. Any ideas? Also added tech-ron complete fuel system cleaner yesterday.

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Ok any improvement at higher rpm under load "driving"? As symptoms disappear we can narrow down the last issues . If is down to the no idle. Sounds like the idle circuit may be plugged. The carb is just a series of different circuits that kick in or out depending on throttle position and vacuum. If you have an idle enrichment screw remove it and try to blast some carb cleaner through it. I haven't seen a Hitachi in forever so I am not sure how accessible that is.

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Sorry but you made me laugh a little... gotta luv things like that..

I've ran into a couple wtf moments too with my 521 rebuild. To me it looks like that needle might be important... any chance it's stuck inside the carb?

Or is it straight up missing...?

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I think it's missing forever

 

nfnm9Hl.png

 

But while I had the anti-diesel solenoid out I took out the idle mixture screw and shot carb cleaner through the solenoid hole out through the idle mixture screw. Some crap came out and I cleaned it up and reassembled. Now it idles fine and doesn't "studder/bog down" past 3k RPMs. I drove it for 35 mins on a mix of highway and city seemed to be back to running right but We will see how long this last.

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I prefer to find something like that, at least you found something that you can verify was wrong...

Missing part and crap in the line ...

it's running so that's good...

i have no idea what the solenoid really does, don't have on my carb....

Probably blocks the fuel flow somehow in the carb when the engine shuts off...

I'm sure some one will chime in if it should be replaced or if your good to go..

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I don't think solenoid it the best way to describe it. It's more like an electro-magnet. When energised it overcomes the spring pressure and attracts the needle into its sleeve allowing fuEl to flow to idle mixture screw. When off the spring pushes the needle back in to carb and blocks fuel for flowing. I guess if it's broken you could remove the needle and run the engine still but you will get some diesel.

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How's your gas tank?

I had an issue where my gas filler neck was deteriorating.... every time I filled up pieces would get washed into my tank...

I never saw in my fuel filter because they were bigger than the pick up tube...

So they would just plug the end of the tube.... engine would stall, piece would float away engine would run again...

I ended up driving with a fuel pump cutoff switch... when it would start to die I would throw it in neutral, kill the fuel pump, hit the brakes to slosh the gas, fuel pump on keep driving.... eventually replaced the filler neck tube....

 

This was my 521 and it would happen at random....

Does your problem also happen while driving at speed or does it seem to only happen when coming to a stop or just idling?

 

If it's only at idle, maybe the fuel pump is on its way out, or you have an issue with your idle settings in the carb....

 

Does it start right back up after it stalls?

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I drove it today a couple of time, it didn't stall once. When is does do it, it happens when I am stopped at idle or I press the clutch in and RPMs drop to idle whilst I'm stopping. Another old problem to rear it's head today was when I go to start the truck I get a single click and nothing. If I put it in gear and let off the brakes and let the truck rock back slightly, then i put the brakes back on and press the Clutch in, it will start right up. Both times today I parked on a incline idk it that has something to do with it or just coincidence.

 

In other news: I fabricated switch panel for the truck (most the wiring harness has been destroyed by PO). Here is a before and after. Haven't put in any switches yet because I'm still deciding on layout and how may switches I'll need

 

Before.

 

7hedDXF.jpg

 

After

 

y2wjLN8.jpg

 

NB0Tg1O.jpg

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Maybe a dead spot in the starter? Are you saying that you roll started it? Check for voltage at starter and just park on hills.

 

Good work man! Nice to see the progress you are making. I am thing that you need to just keep working the junk out of the fuel system.

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What are the two holes for on the vertical brass tube in the picture a few post up?

 

Looks like an electronic feedback carb. That is a solenoid that is part of the primary barrel. It adjusts the fuel mixture 10 times a second with feedback from an O2 sensor. The holes let gas in presumably.

 

 

 

 

 

 

I sprayed out the idle mixture screw and it started and idled for about 1 minute the idle got shitty and finally stalled. I also pulled out the anti-diesel solenoid and it looks like this

 

qlcVOWp.jpg

 

Shouldn't it look like this? With the needle.

 

1qOxJAs.png

Yes but it will pass gas without the needle.

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Maybe a dead spot in the starter? Are you saying that you roll started it? 

 

No I didn't roll start it. I think I just turned the flywheel alittle bit. I'm thinking that the teeth on the starter are binding somehow and turning the engine alittle allows it teeth to unbind. 

 

I'm thinking about rewiring the head lights(high and low) I might do trun signals also although (strong maybe) going to put I switch for blower motor so I can have defroster for when it's raining. I try to figure out the heater For winter. Another strong Maybe is to get rid of the key ignition and do a switch start (with a hidden kill switch, these trucks are REALLY easy to hotwire)

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On the starter is a small Black/Red wire that energizes the solenoid. Make sure it's clean and snug fitting. 

 

Are the battery cables tight on the battery posts? Are the other ends on the intake (negative) and the starter (positive) clean and tight?

 

If it does this all the time it could be a weak start signal from the ignition or the solenoid is packing it in.

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