l20 very poor mpg

[solgroms]

I noticed yesterday that my truck was getting really bad MPG, its a stock l20 with a weber 32/36 4 speed. its only getting around 7-9 MPG with a combo of city and highway driving.

 

[Draker]

What do your spark plugs look like?

[TENDRIL]

sounds like a tune up would add 10 mpg, how old is the exhaust?

 

and is your carb jetted properly ?

[solgroms]

Carb is jetted properly, the plugs are coffee and cream colored. I just had the carb tuned about 2 weeks ago by a trusted shop. the exhaust is a poorly welded on thrush turbo, its got a pretty bad leak where the pipe meets the muffler. could that be my problem?

[datzenmike]

I would say the choke is on but tan colored plugs don't support this. Do you have a locking gas cap.. maybe someone siphoned a few gallons out over night or at work?

 

You don't mention poor performance, because 7-9 MPG would run like crap if it was choke on, dirty plugs, timing, valve lash out of adjustment. If it seems to run normally I would suspect missing gas maybe a leak?

[solgroms]

It runs great, starts fine, drives fine. nobody siphons gas from my truck because im parked in a private parking lot. i was thinking maybe a gas leak somewhere, but it doesnt smell like a gas leak.

[TENDRIL]

faulty odometer ? 

[cruznude]

I don'y know but I owned a ford bronco which only got 10 miles to the gallon and so;d it when gas was 3.50 a gallon. I have a 32/36 on my 620 and really have not notice too much of a drop and I lead foot it all over

[sebpv]

Do you go from full to empty or partial fills every time? How much gas do you put max?

[hobospyder]

use gps on your phone to check actual mileage and see if the odometer is faulty in the truck

[Draker]

I think I got like 17 mpg on my l20b with a 32/36. I would even call that bad mileage. Something is certainly not functioning right.

 

It'd be nice to know what jets are in the carb. But really... if the plugs are golden brown.. that's probably irrelevant. 

 

You might be losing gas.. somehow.. or your gauges are wack. 

[banzai510(hainz)]

i get about 20  this is normal for a 60/70s vintage L motor untill the 5 speeds started comming along

[5t341tH]

i get an adjusted 17mpg on my 32/36 with a 3 speed auto. actual calculations according to odometer is 20mpg, but I have to compensate for the difference in actual speed and displayed speed. this is 60/40 freeway/city

[KoHeartsGPA]

Someone is making away with your gas, I get 15mpg on a fresh l20b with a monster 48mm single side draft mikuni, get a locking cap on there!

[Burabuda]

i get about that same mpg with dual sidedrafts and balls out driving

 

maybe your brakes are dragging?

[banzai510(hainz)]

monster 48mm single side draft mikuni??????

 

thats it right there. hit the accel pump bam gas shooting!!!!!!!!!!

[solgroms]

timing was off, exhaust was also clogged. thanks guys!

[Draker]

timing was off, exhaust was also clogged. thanks guys!

 

thanks for reporting back! Good to hear you got it fixed.

[solgroms]

the muffler filled with unburned gas from the bad timing and it backfired and blew up the exhaust! no joke! now the timing is fixed and the exhaust, my datsun fixed itself!

[5t341tH]

thats great. I wish I can find out where my gas is going....