02 EV fueling issues

[PNWThom]

I’ve recently acquired a 2002 EV with around 40k miles (speedo says 21k but PO says it was replaced). It’s been suffering from a low RPM stumble/sputter through the air box and pretty annoying overrun backfire once it’s warm. Also only getting around 27 mpg and the low fuel light is constantly flickering; I ran it out of gas at 130 miles because even when empty, the light would still turn off with a little throttle twist. Not sure this is related to the backfiring and poor mileage but thought I’d mention it.

I’ve been replaced the air filter (full of seeds!) and reverted the drilled air box lid and mufflers back to stock, as well as new plugs, wires, air and oil temp sensors, without any effect on the running or mileage.

So, what’s the common wisdom here? TPS? I’m pretty new to fuel injection, I never had to do anything to my old Breva except change this oil. I haven’t checked the valves yet but will get around to it soon. I also bought a new fuel pressure regulator but with the cursory look I took when the tank was off I couldn’t figure out how to get the old one out of the housing and I... wanted to get the tank back on. I did try spraying some WD40 around the throttle bodies but couldn’t find any vacuum leaks that way. Not ruling it out though.

Appreciate any advice!
Thomas
Bellingham WA

[Kiwi_Roy]

Can you hear the fuel pump over the engine at idle.
Remove the petrol cap, at the lower point you will see a drain hole about 1/8", dribble some light oil or gas into the moat and see if it is able to get away or is it plugged off?
Which ECU do you have, a P8 or s small 15M?

[s1120]

Id start by checking out the TPS first. They do fail at times.. 

[pat80flh]

I've got a 2000 Bassa.   Low fuel  light is junk, long disconnected.  Poor fuel economy was solved with TPS adjustment, I'd suggest gettting the cables to connect....Guzzidia g.......     When I first got mine the intake rubbers were badly cracked and the rubber coil mounts were broken letting the coils flop around

[Wayne Orwig]

If you have the external fuel pump, and I'm not 100% sure on that year, then check to see if the fuel sensor wire and fuel solenoid wire are swapped. That can do odd things.
I would get GuzziDiag for sure , or someone near you that has it, and run some tests. Check the TPS first.

[TejasNW]

If you have the external fuel pump, and I'm not 100% sure on that year,

Fairly sure '03 is when they went to the internal pumps. 

[Vagrant]

99.9% TPS!

[pehayes]

Poor fuel economy?  By this time, the engine temperature sensor was built directly into the right side cylinder head.  The sensor was housed in a poor, plastic housing which heated-hardened-fatigued.  If it is cracked the sensor doesn't transmit heat appropriately and fools the ECU into always thinking you have a cold engine.  Hence over-rich and poor consumption.  There is a retrofit brass housing to re-secure the temp sensor and correct the issue.  Perhaps someone can point  you to an old discussion thread on this issue.

Patrick  Hayes
Fremont CA

[PNWThom]

Poor fuel economy?  By this time, the engine temperature sensor was built directly into the right side cylinder head.  The sensor was housed in a poor, plastic housing which heated-hardened-fatigued.  If it is cracked the sensor doesn't transmit heat appropriately and fools the ECU into always thinking you have a cold engine.  Hence over-rich and poor consumption.  There is a retrofit brass housing to re-secure the temp sensor and correct the issue.  Perhaps someone can point  you to an old discussion thread on this issue.

Patrick  Hayes
Fremont CA

Thanks- I did run across this in a few threads, replaced the sensor and promptly cracked the housing which I was able to bodge back together (I think). Do you know of a source for the brass housing? I haven’t been able to find one online.

I will say though that the plugs seem to indicate lean running rather than rich... might it be lean at some points in the mapping and rich at others?

[Tom H]

2002....I'm thinking external pump and Hydro.

All good suggestions.

Backfire. Make sure all your exhaust joints are tight and not leaking. Also check the manifold rubber between the head and TB. If not solved,  tune could be the issue as well.

Low speed stumble. If you know the history, that's a good start. If not, you might need to start from scratch. If I'm right and it's a Hydro (per the parts list for your year https://www.thisoldtractor.com/mg_manuals/spare_parts_catalog_california_ev_2002-05.pdf) you don't adjust the valves.
Manual for your bike I think: https://www.thisoldtractor.com/mg_manuals/workshop_manual_california_en_de_ne.pdf
Manual update: https://www.thisoldtractor.com/mg_manuals/workshop_manual_california_update_en_de_ne.pdf

If the TPS is messed up/with or the TB assy has been messed with or the TB's out of sync. this could cause your stumble. This is the manual I recommend for setting up the TB assy as well as TPS. I prefer to go by what the first one says.
https://archive.guzzitech.com/EVTuneup-Jeff_B.html

And with pictures to let you know what the items are that the fist one is talking about.
https://bradthebikeboy.blogspot.com/2012/10/throttle-position-sensor-setting_21.html

Guzzidiag would be great to have, but for now you could just get away with a multi meter and carb balancing gauge.

Good luck,
Tom

[Guzzidad]

  An 02 is not hydro

[pehayes]

Do you know of a source for the brass housing? I haven’t been able to find one online.

I will say though that the plugs seem to indicate lean running rather than rich... might it be lean at some points in the mapping and rich at others?

Apparently Harpers has them but their site was recently hacked and under reconstruction.  Call Curtis by phone to ask for 30163301.
1-816-697-3411
curtis@harpermotocom

You mentioned have very low fuel mileage rates.  A lean running condition would yield very high mileage.  Rich running would yield low mileage.

Patrick Hayes
Fremont CA

[Kiwi_Roy]

I asked about a noisey fuel pump.
If the filter plugs off with rust the fuel pressure goes from 40 to 70 PSI the ECU cannot compensate for this so the result is more gas or at least until it plugs off all together, I had this occur to an EV I rode back from Denver to Vancouver.
When I picked it up from the previous owner I noticed the racket the pump was making but I had no reference, later in the trip I back flushed half a cup of rust out of the filter and it never looked back.
Patrick made me aware of the blocked drain issue that causes the tank to rust.

[Dilliw]

Check the TPS and check for exhaust leaks especially the crossover muffler.

[PNWThom]

I asked about a noisey fuel pump.
If the filter plugs off with rust the fuel pressure goes from 40 to 70 PSI the ECU cannot compensate for this so the result is more gas or at least until it plugs off all together, I had this occur to an EV I rode back from Denver to Vancouver.
When I picked it up from the previous owner I noticed the racket the pump was making but I had no reference, later in the trip I back flushed half a cup of rust out of the filter and it never looked back.
Patrick made me aware of the blocked drain issue that causes the tank to rust.

The fuel pump sounds normal to my ears... I do have a new fuel filter I haven’t gotten around to yet as well as fuel pressure regulator (is there a trick to getting it out of the housing??) I guess those are my next step before messing with the TPS. I don’t think the exhaust is leaking anywhere but I’ll double check that as well. As I said the plugs look lean to me, white on top though not more than I would expect. My only other mechanical experience though is on old british sports cars so my perspective may be off. Thanks all for the suggestions!