wont stay running while driving

[80datsun720]

okay, i have a pickup that wasnt treated well at all when i bought it, its had a problem when at 55-65 it would lose power and eventually die out, didnt think much of it but i never took it on the interstate or highway after that, well lately its been doing it when im in town too, it only does it when its completely warmed up. any suggestions?

[wayno]

Welcome to Ratsun  B)

 

Check your fuel filters, sounds like one is plugged.

Do you have a weber carb?

Webers have a screen/filter under the fuel inlet in the photo below.

The filter is in the big nut on the bottom, remove it, clean and replace.

[80datsun720]

thank you, and nope its completely stock from what i know and it feels like it driving it too, ill check the filter out though

[80datsun720]

but then again that wouldnt make sense with it being the fuel filter plugged, because it runs fine when its cold and starts acting up when it warms up

[datzenmike]

Wayno means plugging up. The harder you drive or the faster you go the more gas your engine needs. The flow through your filter may be restricted and allows lower speeds but not out on the highway. I had a new '76 B210 and didn't drive much on the highway, but when I did I noticed my top speed was only 70. Months later it was 60 and then I noticed it had trouble climbing a hill. All wer high demands for gas that couldn't be supplied and the carb was running dry.

[wayno]

but then again that wouldnt make sense with it being the fuel filter plugged, because it runs fine when its cold and starts acting up when it warms up

 

You need to keep in mind that when an engine is first started, everything has settled from the night before from no activity, so any filter/screen that had been sitting without flow or suction, the stuff settles/falls off the screen/filter, so when you start it, it can get fuel again.

When you are not on the hiway running your engine at sustained rpms, it doesn't use as much fuel constantly, so the fuel pump can keep up, but when you get on the freeway, it can't get enough fuel and starts loosing power and it can actually die, once it dies, the suction is lost, the crap on the filter/screen falls off, and you can get fuel again for a while.

 

Inline filters will tend to just plug up and not allow fuel threw anymore, I have had them get sucked flat on my diesel, but carb screens are differant, when the suction is lost, the fuel that got past the screen, but didn't get to the engine just on the otherside of the screen can move backwards and clear the screen a little.

 

I don't know if stock datsun carbs have screens in the inlet of the carb like webers do, but it is cheap to replace fuel filters, so replace any you have and see if that fixes the issue, if it doesn't, well at least that is not the issue for sure.

[80datsun720]

i understand all of this but how would that explain it running and driving fine when its cold but acting up when it gets to operating temp?

[wayno]

i understand all of this but how would that explain it running and driving fine when its cold but acting up when it gets to operating temp?

 

Maybe the choke being closed and cutting half the air off makes the fuel mixture work.

I am not saying that fuel filters are your issue, I am saying they could be your issue, and new fuel filters are cheap, and easy to change.

[80datsun720]

well, the motors about shot so i think its time for a build soon(:

[nsackett]

i had the same issue with mine, my electric choke was actually stuck shut, and wouldn't open when the motor warmed up, try zip tying your choke flap open and see if it makes a difference. or replace the electric choke with a manual choke, which is what i ended up having to do.

[ggzilla]

A motor that is smoking heavily will still run well

A rebuilt motor with the same accessories will still run bad.

 

... find the problem and fix it

[banzai510(hainz)]

change the filter first its cheap.

as for the motor shot comment dont mesn nothing it was still running.

 

if you changed soemthing and didnt tell us , tell us now. Maybe the coil is getting hot.

 

when it goes bad you could pour soem fuel in there and see if it runs then. or ck for spark.

 

ck for a cracked hose right before in the fuel pump if a manual pump.

 

ck the valve lash. maybe its starting to get tight.?

[80datsun720]

bought a new truck so this is gonna be a project truck, not a fan of four cylinders at all, probably gonna do my best to see if i can get a small block or a fuel injected v6 in it, any ideas on how much of a pain in the ass converting it would be?

[ggzilla]

Not worth it. Sell it and buy a truck that has a V6

[kelowg]

More of a pain in the ass then fixing what u have. Motor spot, how so??

[ColtonMelson]

Whamp Whamp Whamp.......