It's Running Great.....or so I thought

[Faulkner34]

Hello Everyone,

I had my first true Land Rover "experience" this past weekend. After rebuilding the Rochester single barrel carb, tweaking the idle adjustment and the air/gas mixture adjustment, replacing all vacuum lines, and adjusting the vacuum advance (I also have new plugs and a new fuel line / filter) this past Friday my Rover had a level of power I hadn't experienced since purchasing it.

With all that confidence I decided to drive it 30 miles to a local British Car Show on Saturday. It ran beautifully (and got up to 55 mph!) for 29.9 miles until I reached the car show registration line. As I slowed down to an idle to wait out the line it died and wouldn't start again. I then had the humbling experience of being pushed into the show fairgrounds and into my parking spot (needless to say I didn't bring home any trophies!).

While at the show I adjusted the idle screw on the carb slightly and it started right up and made it all the way home after the show. However, the drive home didn't feel the same, it felt like it was giving out at times in 3rd and 4th gear. It never died but just didn't exude much confidence.

The last two days it has started easy and runs well WHEN CHOKED. Once the choke lever is pushed back in it sounds like it is going to die every time I hit the accelerator. If I rev the accelerator a bit it will get up to speed but if I am in a situation where I have to hit the accelerator hard it will die unless choked.

So with all that said, does anyone have any suggestions as to what to try next? Should I replace the Rochester with a Weber?

Any help you can provide is appreciated!


Jason
'73 Series III (88")

[bugeye88]

Jason,

Just my 2 cents, but it sounds like all the stuff you did with the Carb etc was good, and it ran better initially as a result, but after that it sounds like 1. you were experiencing vapor lock while in line for the show 2. your leaning out the mixture at the show after it cooled down is too lean and does not give the engine enough fuel to have power without having the choke pulled to give it a richer mixture. My advice would be to fit an electric pump after the mechanical one (between the mechanical pump and the carb) You can put an on/off switch in the cab so you can turn it on and off if you wish. I have this setup and it eliminates vapor lock for me. As for the carb itself, I'd get it back to where you had it when it was running good on the way to the show.

Cheers,
Rob
Bugeye88

[o2batsea]

If you aren't an experienced carb rebuilder with the specialized tools, and an ultrasonic tank to clean parts with, then you probably wasted your time. Hate to say it but the best way to rebuild a carb is with a new one.
That said it would seem that your idle circuit still has gunk in it, and you may have a bad accelerator pump. Pull the thing off and blow some compressed air thru all the passages again, and put it back together. Also check the condition of the tank. If there's a bunch of poop in it, then you will just keep sucking hate into the carb whether it's new or not.

[bugeye88]

Jason,

Like @sea says, look at the tank and check the fuel pick up tube and its screen (if its still there) look for gunk. Also run an in-line filter after the fuel pump and before the carb. Check the fuel bowel on the mechanical pump also. It will have a bunch of crap in it too if the tank is full of gunk.

Cheers,
Rob
Bugeye88

[Faulkner34]

Thank you both for the feedback. I forgot to mention in the post that I have also installed a new fuel tank, fuel pump (no gunk in the bowl), and in line fuel filter between the pump and the carb. I will look into an electric pump as bugeye suggested



Jason,

Like @sea says, look at the tank and check the fuel pick up tube and its screen (if its still there) look for gunk. Also run an in-line filter after the fuel pump and before the carb. Check the fuel bowel on the mechanical pump also. It will have a bunch of crap in it too if the tank is full of gunk.

Cheers,
Rob
Bugeye88

[siii8873]

also check for a vacuum leak, this could explain need for choking it, running lean. Also did you replace the fuel filler cap? I had similar issue due to a new fuel filler cap, new one was a sealed cap, unvented which caused a vacuum in the tank limiting ability of fuel pump to pull fuel under load.

[I Leak Oil]

Mixture?

[Faulkner34]

I checked for vacuum leaks and didn't find any. I didn't change the fuel filler cap and believe it still has the original one. I will check to see if it is vented though - thanks



also check for a vacuum leak, this could explain need for choking it, running lean. Also did you replace the fuel filler cap? I had similar issue due to a new fuel filler cap, new one was a sealed cap, unvented which caused a vacuum in the tank limiting ability of fuel pump to pull fuel under load.

[Faulkner34]

Hi - are you referring to the air / fuel mixture? Can you provide a little more information?


Mixture?

[I Leak Oil]

Yes, air/fuel mixture. I assume the carb you have has a mixture adjustment? Get it to operating temp and adjust accordingly.

[darbsclt]

Even in my short experience with Rovers... I found that your symptoms can be caused by a number of issues. Eagerness to solve it might temp you to try and "correct" the problem from many directions at once. I've already read "new Weber" and "new electric pump."

My advice, novice that it might be,... list out the likely culprits and systematically rule them out one by one - before moving to the next. Assume nothing - just because a bit is new (or has been replaced) doesn't mean it's not the issue.

Fuel lines & pump -
First: inspect all lines, tighten all connections... just because it's not leaking fuel doesn't mean air isn't entering the system somewhere.
Next: disconnect line from carb, place in mason jar, crank engine... Is there a good/steady flow?
Next: reattach line & insert fuel pressure gauge, start engine... Is there good pressure?... is it consistent?

You get the idea...

Then move on to the carb. The Rochester is a good carb... it's what I use... I wouldn't be quick to give up on it. I do read, however that it likes low(ish) fuel pressure and high volume.

Then move on to timing; something I haven't heard (read) mentioned... etc...
Don't forget... even a bad coil might cause 'fuel starved' symptoms.

After spending $$$'s throwing new parts at my series in an attempt to fix a similar problem... I cured it (mostly) with a $3.00 filter (sigh). Lesson learned...

Good luck!

[Faulkner34]

Thank you for the great advice!

I have heard others say they would stick with Rochester as well. Is there a particular position you have found the air / fuel mixture screw works best in? I think I read a general carb blog online that said to turn the screw in until it is lightly snugged then unscrew 1.5 turns. Does that sound about right based on your experience?




Even in my short experience with Rovers... I found that your symptoms can be caused by a number of issues. Eagerness to solve it might temp you to try and "correct" the problem from many directions at once. I've already read "new Weber" and "new electric pump."

My advice, novice that it might be,... list out the likely culprits and systematically rule them out one by one - before moving to the next. Assume nothing - just because a bit is new (or has been replaced) doesn't mean it's not the issue.

Fuel lines & pump -
First: inspect all lines, tighten all connections... just because it's not leaking fuel doesn't mean air isn't entering the system somewhere.
Next: disconnect line from carb, place in mason jar, crank engine... Is there a good/steady flow?
Next: reattach line & insert fuel pressure gauge, start engine... Is there good pressure?... is it consistent?

You get the idea...

Then move on to the carb. The Rochester is a good carb... it's what I use... I wouldn't be quick to give up on it. I do read, however that it likes low(ish) fuel pressure and high volume.

Then move on to timing; something I haven't heard (read) mentioned... etc...
Don't forget... even a bad coil might cause 'fuel starved' symptoms.

After spending $$$'s throwing new parts at my series in an attempt to fix a similar problem... I cured it (mostly) with a $3.00 filter (sigh). Lesson learned...

Good luck!

[stomper]

That is what the recommendations are for a webber idle screw. I can't confirm this for the Rochester. Careful reading things online, as there are people discussing solex, zienith, webber and rochester carbs. Make sure what you are reading is specific to the rochester.

[I Leak Oil]

You can probably find a manual for your carb on line as well. That will explain exactly how to set it up.

[darbsclt]

Thank you for the great advice!

... Is there a particular position you have found the air / fuel mixture screw works best in? I think I read a general carb blog online that said to turn the screw in until it is lightly snugged then unscrew 1.5 turns. Does that sound about right based on your experience?

Thanks, although I have a Rochester fitted... my experience mucking about with it is limited. In short... it's always worked great (lousy milage... but that's another issue). When it came to fixing my "starved fuel" symptoms... I placed the carb last on my list; convinced that carbs (in general) are near-maigical devices, requiring much care & caution.

That said... I have collected an assortment of service manuals pertaining to the Rochester - in anticipation of needing to tear one apart someday. I just tried to attach one of the manuals (1.6mb pdf)... but it's too big for this forum. In any case, it confirms that 1.5 turns is the correct starting point.

If you would like me to send you a pdf service manual... reply (or PM) with an e-mail address.

Good luck!

[SafeAirOne]

You can probably find a manual for your carb on line as well. That will explain exactly how to set it up.

Was about to suggest the same thing. I just perused the "Servicing GM Model "B" Carburetors" manual online. Very informative as to set-up.

If the OP needs directions to the online manual, just PM me and I'll point you in the right direction.