257 cc Linhai Won't Start or Fire After Fuel Pump Replaced
 

Hi there.

I have a 257 cc Linhai on a JCL 260. I replaced my vacuum fuel pump with an electric one since it was running short on fuel at high speeds with low vacuum. It appeared to run good. I took it for a test ride for 80 miles during which it ran great until it died. It won't start or fire after this.

I am trying to get it going again. I can hear my electric fuel pump running. Fuel drains out the drain for the carb bowl when I open it. When I take the spark plug wire off then hook it to a different spark plug that is grounded I get spark when I turn the engine over.

I'd appreciate any help I can get to make it fire and start. Any ideas where to go from here?

Thanks for your help.

diffrent plug????.... why not take the one out of
the motor and see if it sparks... after all it's the one
you are using to try and start the motor...

what is the out put PSI of this new electric fuel pump..
It could be over riding the float valve if the PSI is to high..



..

What's the voltage reading? Those igniter relies on stable DC source...
---
The trick for those DC mystrey black box http://translate.baiducontent.com/tr...en=&monLang=zh

Hi Bob, what are you riding? I'm unfamiliar with a JCL 260. Is it a scooter?

Thanks for everyone's help. That is what I need.


The fuel pump is a Facet 40105 the details of which can be seen here:


http://www.facet-purolator.com/cube-fuel-pump-kits.php


and here:


https://www.aircraftspruce.com/catal...facetpumps.php


I will pull the plug that is in the cylinder as a next step to see if I get spark


The electric pump has a pressure of 3.0-4.5 psi and a flow rate of 30 GPH.


The battery is fully charged.. Ignitier??? I am not sure I understand. It turned over fired started and ran before this change.


The JCL MP250A is a scooter with a Linhai 257 cc motor. You can see more details here:


http://www.jclusa.com/MP250A.htm

Anyone have any ideas how I can get this going?

I'm wondering if the electric fuel pump is enough to unseat the float valve.


One thing I dislike about modern scooters is the vacuum-operated fuel pump. It seems to me that the design is due to the bodywork that precludes a typical fuel petcock. The bandaid vacuum pump stops pumping when the engine stops running. All great in theory, but a nuisance when they fail or run out of fuel at low vacuum.


Do you have a way to ditch the fuel pump and add a petcock? That should provide a steady supply of fuel at gravity pressure, assuming your tank is higher than the carb.

The tank is lower than the carb so gravity won't work here.

Could you go to a better quality vacuum pump, like a Honda product? I replaced enough vacuum pumps on a friend's China scooter to know I don't trust them. Fuel would often leak through the China pump and fill the crankcase with gasoline.

The problem isn't that the vacuum fuel pump failed. It is that at high rpm vacuum is too low to drive high volumes of fuel with a vacuum fuel pump. That is why I went to the electric fuel pump.

I'm with you on that. I'm wondering if a Honda vacuum pump might have a different spring rate than a China vacuum pump that would allow high RPM fuel flow. It's only a theory.


For now, have you considered putting the stock pump back in, to confirm that nothing else is causing the symptom?

I agree with Weldandgrind. This may not have been a fuel pump issue. could be that you may need to up the main jet size or valve adjustment. Have you checked the valves for adjustment? They may be set to tight. Does it fire up after you changed the spark plug?

Right now I don't understand why it won't fire. I have fuel in the bowl of the carb when I open the drain hose.


It seems like it is something simple I am missing. It ran real good for 80 miles then died and now wouldn't fire.


Both WeldanGrind and Pete asked about the fuel pump pressure could overpower the float. At what PSI would something like this happen?


I may have to go back to the vacuum fuel pump but need to eliminate everything else first.


What would cause it not to fire when there is fuel in the carb bowl?

JerryHawk250 I missed your post while I was writing my last one.


The valves were adjusted twice and it made no difference to the fuel flow at high rpms issue. The spark plug is a new one, the same one that it ran 80 miles with and ran real good.

May have already been asked/answered but will it fire if you squirt a little gas into the cylinder or spray a little starter fluid in the intake?



/

Have you tried a different plug? The new plug could be bad.

I removed the vacuum line from the intake manifold so I could spray starter fluid down the hole while I turned the engine over. Unfortunately my battery (relatively new) is shot.


I boosted the battery from a known good battery. I am getting 12.5 volts on the scooter battery when boosting. When I turn it over when while boosted and spray starter fluid in the intake manifold it wouldn't fire.


What should I check next? Is this a good enough test since the battery was shot while I tested it?

Fuel-Spark-Compression . . which aspect is deficient?

http://www.youtube.com/watch?v=-bh_f0ACQ_k

Anomalies include a sheared crankshaft-flywheel woodruff key, which throws off timing . . and possibly a 2-bolt intake valve cover orientation issue.

Hate to say it, but unless china did something stupid with the fuel pumps, you can run a 750cc lawnmower engine wide open on a vacuum pump.....john deere does it every day..... crank case pressure should be driving the pump off the crankcase vent, and that will rise with more rpm....

If it wont fire on starting fluid, i would be checking compression, if thats good, i would get a new CDI box/ignitor... you may have spark, but is it 1. Strong enough to ignite under pressure 2. Sparking at the correct timing. China is known for cheap unreliable cdi ignitions....

Thanks for everyone's help with this.


The battery was low. I was charging it until it said it was full but wasn't checking the voltage. I replaced the battery and fully charged the new one.


Fuel, Spark and Compression. I checked spark by pulling the new spark plug and grounding it while turning the engine over. I had good spark. Next I measured compression. Compression is 50 psi dry. There's your problem.


What next?

well, triple check your valve clearances. other than that, start with pulling the head. if one of the valves is bent, theres your compression leak. if its not one of the valves, its your piston rings. i would recommend doing a new piston at the same time as the rings, since they are most likely stuck in the piston. thats what happened to my 200cc roketa... stuck the rings from (my guess, not 100% sure) poor maintenance and overheating. there was carbon caked in the ring grooves of the piston, wedging the rings so they couldnt spring out to the cylinder walls and do their job...

I just put a new piston and rings in. What other things can I check before I pull the head? Make sure the timing is correct, check the valve clearance....

if you only have 50-60psi compression its either your valves or your rings, or your head gasket, which would become apparent as soon as you remove the head. also, did you have the cylinder honed to cut the new rings into the bore?

if you can get a Leak down tester (loaner tool from an autoparts store) that has the correct thread for your spark plug, thats the best way to diagnose low compression. hook it up to an air compressor, air everything up with the piston at top dead center of the compression stroke so all valves are closed, and make sure the crank cant move (breaker bar and socket on the crank nut or similar) and listen for leaks. if you only have 50-60psi, you will hear the leak..... if its coming from the crankcase vent, rings.... intake, or exhaust, its one of those respective valves.

Given the fact that I just had it all apart aren't the odds higher that some step hasn't been done correctly higher? For example valve adjustment, timing off, timing chain not put on correctly, what else...?


The valves held gasoline when I had it apart. The piston and the rings are new. The gaskets are all new.

Possibilities are endless...LOL its possible that your intake gasket didnt seal quite right, ran it lean, and burned a valve.... also, did you properly torque the head gasket? Also did you check the head surface for flatness with a straight edge?

Just going over the things i would in my head (i am a small engine/compact diesel mechanic....)

Still cant rule out stuck rings either..... easiest way to check that is pour a tablespoon or so of ATF fluid into the cylinder, spin the engine over (by hand if at all possible) to work the atf around the rings, if they are stuck and not too badly, they should free up and give your compression back, at least more than 50 psi....LOL

Oooh, one more thing...LOL Can i ask why the piston was replaced recently? What was the original failure? That may help the diagnosis... also, if you can post a video of what it sounds like when its turning over (with spark plug in) it may help as well....

More questions as i think about it.... is this an overhead cam engine? If so, do your timing marks on the crank and cam still line up? If one of the valves is open at the wrong time it will fubar your compression (obviously...LOL)

Just got back from O'Reilly's. They don't have a leak down tester in their tool loan program. I will look around for someone else who does.


The compression test result I gave was with a Harbor Freight gauge. Is that an issue in any way? Is it worth me getting a compression gauge from a tool loan program and retesting before starting other steps?


The head gasket was properly torqued following the shop manual. The head was placed against a steel straight edge and I saw no warping at all.


Single overhead cam with 2 valves which is water cooled.


I thought they lined up when I put it back together but that is why I asked the question. I can't see both marks without tearing everything apart again. There are two set of marks to line up. One on the sprocket of the timing chain which is covered up unless I pull everything apart again. The second on the CVT which I can get to with the engine assembled. So I might be able to adjust the valves without pulling it apart by finding TDC by the highest piston position with the two marks on the CVT aligned. I was careful and followed the shop manual.

Here is a good summary of how to do the valve adjustment so you can see how it looks:


http://www.chinesescooterreference.c...Adjustment.pdf


The engine is essentially a Yamaha YP250

bogieboy? Anyone?

i would double check the timing first off, then try the ATF down the spark plug and try the compression test again... it wouldnt hurt to double check the compression with a different gauge, because i have a comression tester from HF that doesnt always read right.... i have to clean out the shraeder valve in the end of the hose for it to work properly. however it was reading 0 psi...

Thank you sir.


I will try the ATF in the cylinder hole followed by a compression test.


Could you elaborate more what you mean by check the timing. Right now everything is together engine and all the body panels. If you mean check the marks on the camshaft sprocket (see page 10 of the following document) that is a fair amount of work and I would like to make sure we check the other things first before diving in to it. I can easily check the second set of marks on the shaft that drives the CVT (see page 11 of the following document).


http://www.chinesescooterreference.c...Adjustment.pdf


Checked and these guys don't have a tool loan Leak Down Tester: O'Reilly, Auto Zone, Pep Boys, Advance.

Just did the compression test again. Here are the results:


60 psi dry
60 psi after putting ATF in the cylinder before the compression test

looks like a tear down is in order.... something went wrong, and its really hard to guess at what it is without pulling things apart.... start with timing, like the whole document you posted, start fresh, then if that checks out, time for the head to come off to check the rings and head gasket.

Thanks bogieboy.


A couple of questions. First is it worth redoing the valve adjustment before pulling it apart? I can do the valve adjustment and be at top dead center by putting something in the cylinder and checking the marks on page 11 of this document. I can't see the parks on page 10 of the document without pulling it apart.


http://www.chinesescooterreference.c...Adjustment.pdf


Does the fact that the compression is the same dry and with ATF tell us something?


Is there anything else I can try before I pull it apart?

I would redo the valve adjustment. Just make sure your at top dead center. It sounds to me like you might be 180 off.

Bob, I recommend that you repeat the compression test with the valve cover removed.

We are going to get this thing going soon! Thanks for everyone's help.


bogieboy do you agree that I should try a valve adjustment before taking everything apart again? Is there anything else I should do before doing that?


WeldanGrind why do you recommend doing the compression test with the valve covers off? Intake, exhaust or both?

My guess for WAGs suggestion is to see if you hear chuffing, that would be indicative of a blown headgasket. It cant hurt to do another valve adjustment either, i have had strange things happen on brand new tractors...LOL had one engine that had a valve adjuster back out of a rocker arm in 4 hrs run time, straight from the factory.... you may have a similar issue.... or it just backed out enough to cause low compression ...

Bob, I meant the entire valve cover. If the compression returns by simply removing the cover, my guess is that it was on backwards.

Life got in the way of getting this thing going which I want so much soon. Thanks so much to everyone who has helped with that.

First I reset the intake valve gap then did a compression test since I could do that without removing a bunch of panels. 45 psi very low.I reset the exhaust valve gap to 0.20 mm and did a compression test.Compression was still only 45 psi.

What do I need to do next to get this thing going? I had fuel and spark but no compression. What else could be causing the low compression?Timing chain off by one tooth (this engine has two sets of marks, one on the timing chain sprocket and another on the engine main shaft and both are set right at the same time)?

Any ideas?