Losing Power and Surges

[wagoon]

My dime starts out fine, drives well for a few miles then I notice that after driving a few miles my car starts to surge and lose power but the idle remains the same. It kind of sounds like a lawn mower. For example: I'm in 1st and engage into 2nd gear, it seems like the idle remains at the same rpm on shift change. Here is what has been done so far.

 

Specs: L16

Carb: Weber 32/36 DGVE

 

Recent upgrades: New 2.25" Cherry bomb muffler

Changed the exhaust/intake manifold gasket

 

It can't be an exhaust leak,maybe carb related, clogged fuel filter? I dunno. Any ideas would help, where should I start?

[hobbes_the_cat]

Clogged fuel filter would be the first thing I would check. It sounds like a fuel delivery problem.

[wagoon]

Alright, just switched over to a fresh fuel filter...almost there. I can tell the fuel flow is better. Not solved yet...I drove it around the block to wake up the neighborhood and I noticed almost no bottom end, and shifting to 3rd gear sounds like the lawn mower. Now what? The exhaust does not smell foul like an exhaust leak....but could the exhaust flange go bad? 

[Npdavies.]

If it sounds "like a lawn mower" isn't it possible you aren't running on all four cylinders?
Maybe check your plugs? Hard to say for sure without hearing it.

[wagoon]

Does not sound like a lawn mower literally, but  in terms of continuous idle that surges right after 2nd to 3rd gear shift then pressing the gas...Hope that makes sense. It's almost like it lost of compression or something  is getting stuck in the carb somewhere, having a hard time to keep open or is it staying open. Like I said  it feels strong on start up, it drives real nice for awhile and after a short drive, it goes through this...what ever it is...

[bilzbobaggins]

What was in your old fuel filter?

[wagoon]

Looked really dirty with a few dark items in there, as compared to my new one. 

[bilzbobaggins]

If it got better with the new filter, maybe you got some crap in your carb.  Its easy to clean.  I think ive cleaned mine a dozen times.  Get the little filter thats in the 11/16's?? bolt under the hook up for the fuel line and clean the bowl out.  Dunno tho.  Im not good at figuring stuff out.  Kinda sounds like a vac leak too.  You said you did change the manifold.

 

Good Luck

 

Jeff

[banzai510(hainz)]

Is this still a point ignition?

maybe the condensor or points out of adjustment.

if running points use a wstock coil with the ballast resisitor. any changed let us know. Coil HOT????

 

2.25 ich exhaust??????????? thats why you got no low end

 

recheack the timming.

[wagoon]

No points, Electronic Dizzy...

[620fever]

Almost sounds like a problem I had when I had to remove my stock hardline due to it leaking,and just connected a hose straight to the carb with no return line, are you running the stock metal hard line still or a fuel pressure regulator, if not your fuel pressure might be too high?

[racerx]

how's your coil? maybe secondary going out...

[racerx]

how old is your fuel pump?

[Xnke]

The 2.25" exhaust isn't even remotely close to causing a reduction in torque...if anything, it helps. Backpressure helping bottom end torque is a myth, and one that has been disproven many times by many people.

 

Back to topic:

 

Loosing power and surging sounds like a carb with a main jet full of crap...on the idle circuits they may be OK, but the main jet being clogged will cause a lean condition, which will cause surging under light load and low power. On acceleration, the surge may go away, but being lean will still cause a loss of power and poor running.

 

The fact that it drives OK on warmup means that the engine is probably fine, and as long as the warmup enrichment is working, the engine is not too lean to run...when it warms up the enrichment circuit would kick off and you'd be running on the idle circuits and main jets...which are too lean, for some reason.

 

New fuel filter (Yep, even the one you just put on there, change it too) and pull the carb off and clean it out. Make sure the float level is set correctly, too!

 

Also, check for intake manifold leaks. I don't care if it's Fujibonded onto the engine without a gasket...never rule out a gasket as a problem just because you "just changed it".

[Rays74]

The 2.25" exhaust isn't even remotely close to causing a reduction in torque...if anything, it helps. Backpressure helping bottom end torque is a myth, and one that has been disproven many times by many people.

 

The fact is that back pressure is not the issue, it's exhaust gas speed in the pipe that has EVERYTHING to do with torque. The bigger exhaust you go with, the slower the exhaust gas speed all things being same. Particularly with a small cylinder size like the L16, going too large a pipe will see that exhaust gas being real lazy getting away from the cylinders. This is where you get a reduction in low speed torque/power and likely a small gain way up in the rev range somewhere IF the engine can use it. Making the car feel a little lazy around town too. An extreme example would be a study on 2 cycle exhaust systems......lots of good info and knowledge regarding exhaust gas speed management there ;)

 

This has been talked about on here to death, search exhaust size and L16.

--Ray

[Xnke]

...Yes it has...and the ONLY time that velocity matters is in the primary pipes, prior to the merge. Once you pass the merge, bigger is better...until the pipe outflows the volume of air involved. Just like plenum sizing on the intake...once you are past the main reflection causing discontinuity, the plenum volume needs to be big enough to appear infinite...or at least be filled fast enough to appear that way. Same thing in the exhaust.

 

Lots of data on this guys, and an L20B isn't going to loose power OR torque on a properly fitted 2.25" pipe.

[wagoon]

Im running the stock hard line for now.

 

So even I put a new exh/intk gasket it still may leak? Retorque?

 

Fuel pump is pretty old...replace it?

 

Pull off the carb? Clean the float? Noticed the gasket is a little krinkley...will change.

 

Did I forget anything...exhaust stays for now:)

[banzai510(hainz)]

if the car idles w/o the choke there is not vaccume leaks.

 

its been proven the smaller exhaust is better for torqe. Sport compart Car had a test. Of coarse depending on set up motor. I DGV carbs with a 2.25 isnt going to make 1 oz more torqe.

But this has nothing to do with this current proplem.

Modern High output non turbo imports dont have 2.25 from the factory.

 

get a rahg run up the rpm and put the rag over the carb and maybe it will suck the dir out of the jets(Mexican tuneup)

 

 

My Banzai510 has twin Mikunis and I only run a 1.75inch. 2in would be be better. But its too late now. not ging to change it.

I had a 510 once with a L16 and DGv and I put 2.25 on and sounded COOLEWR at 20yrs old but that was about it.

 

If for this proipplem I start mechnically. Ck the motor cam timming, then ck the vaLVE lash then ck the eleltrical timming, fuel filter. ck the input of the fuel hose for cracks as it can suck up air(like its running out of gas). ck the carb for good squirt. ck the sendary for EZ opening. Idle mixture. speed idle. then ck coil wire , or coil if hot(esp if was changed with a wrong type coil) Cl dizzy for slop. a tiiimg light might cath this.

 

make sure the alternaotr is charging good.

[wagoon]

I have been noticing that on startup, the head makes this ching a ling sound, and after I rev a bit for a sec it goes away. I saw it on the forums the info somewhere but can't seem to find it. I know I need to do a valve lash on her. Do you have a link on how to do it? Where did I see that at....there was a crazy Banzai guy with a headband rocking to some theme music, thats where I saw it. 

 

Would the valve get sticky to make the exhaust valves not open? 

[banzai510(hainz)]

I think Mike Klotz had a better vid on doing the valve lash.Try the How to section? its in there soemwhere or maybe Olddatsuns.com tech section

 

Usually if it makes a noise, its too loose which wont cause a mmissing proplem. Its when its too tight that the compression blows out in to the exhaust and feels/sounds like a missing proplem.

 

what I do if working fast is just run each cam lobe pointing up and if the rocker wiggles a little bit then its good. Unless you got ALOT of wiggle. then tighten it up to keep the noise down.

 

 

 

for me hardest part to troubel shoot has always been the carb. Thats why I got spares and to keep the fuucking around time to a minimum I just pull the 4 bolts and swap another weber on there. If you got a stock carb then most pople dont have spares of those and its just a best guess and cost to get a Weber DGV.

[wagoon]

Just for clarification per Klotz, he said lobes are at 10:2 position, and you say all straight up. I like the straight up rule. But how bout turning on the crank itself, is that at least 180?

 

So just go through (1)(2)(3)(4) all lobes up? My 1st valve lash!!!

 

Oh yeah, are you suppose to remove the plugs as well before doing it?

[datzenmike]

Alright, just switched over to a fresh fuel filter...almost there. I can tell the fuel flow is better. Not solved yet...I drove it around the block to wake up the neighborhood and I noticed almost no bottom end, and shifting to 3rd gear sounds like the lawn mower. Now what? The exhaust does not smell foul like an exhaust leak....but could the exhaust flange go bad? 

I assume with the throttle down the car jumps ahead, snapping your head back,

followed by a dive where your head almost hits the dash, followed by head snapping acceleration and a dive... repeated??? Would that describe the problem???

 

This would be the carb using all the fuel and running dry, pump squirts some in car takes off again, runs dry, pump squirts some in car takes off again.... repeat.

 

1/ This could be the float set too low and hardly any fuel in the bowl.

2/ Blockage at the fuel inlet valve.

3/ Faulty pump.

4/ Plugged filter.

5/ Blockage in fuel lines.

 

 

Easy to check. Floor it until it starts surging and as fast as you can turn off ignition and get the clutch in. Get the motor stopped as fast as you can and pull over safely. Take a look at the float chamber glass on the front of the carb. Empty or close??? If yes it's not getting fuel for one of the reasons above.

[wagoon]

But there is no glass on the 32/36DGVE, how would you check that? Those symptoms are pretty dead on. 

 

I know for sure it needs a valve lash though. 

[datzenmike]

Sorry assumed you had stock.

 

 

Take the outlet hose from the fuel pump off and hold over a pail. Crank the motor over. If everything is working right gas will shoot out in STRONG pulses.

 

If dribble then the problem is the pump or fuel line blocked

If it shoots out then has to be the carb.

[banzai510(hainz)]

10 or 2 or straight up is all fine. as the back of the lobe should be all the same from that position.

 

 

remember ck the fuel hose going in to the fuel pump. If cracked it can suck air. making the fuelpump look bad.

go with Mikes trouble shooting.

 

a tight valve will give a missing cylinder type of proplem so if you think your running out of gas its most likely not it.