The 8V TPS is more of a switch to tell the ECM the throttle position
off idle and WOT, but it isn't a linear resistance like most TPS sensors.
Wild

A 90 might have the TPS switch but 91 on have a real TPS.

The MAP sensor measures absolute pressure which will be high with key off and then drop with load. Vacuum is a relative measurement and will increase with load. Key on engine not running you should read atmospheric pressure which is around 1 bar or  around 29.5in/Hg. For a real FSM (albeit for later models) try here:

http://www.suzukiinfo.com

The range they give is quite wide, but your findings are or appear quite linear
in the results, so I would say the MAP is working as it should.

The range that would be in question should be from low vacuum like 1 to 2 in
and high at about the 15-16 in range, outside of that you don't really need as
your engine will not be producing power at those levels, over 15-16 is a deceleration
condition, no fuel needed, and below 1-2 would be either engine not running (NA) or turbo
boost which you don't have.

Normal WOT vacuum is low but never 0 on a NA engine


The only other thing I can think of is your fuel pressure and or the injector might
be plugged somehow, fuel pressure on an 8V is lower than on the 16V about 34 PSI
at the fuel line on the back side of the TBI, kind of a pain to test, I had to cut my fuel
line and add a "T" fitting to get a reading. I don't know what the manual says to do
to check it, but somehow you are still getting a lean condition, because when you pull
the MAP vacuum line it tells the ECM more fuel, and your truck runs better

Good work so far
Wild

I don't know what the manual says to do to check it, but somehow you are still getting a lean condition, because when you pull
the MAP vacuum line it tells the ECM more fuel, and your truck runs better

Good work so far
Wild

Are you sure about that?  It seems to be the reverse of the what I would expect.

A high vacuum on the MAP sensor would indicate a closed throttle, and as the throttle opens the vacuum decreases (gets closer to atmospheric pressure) - I'm not sure about the Samurai EFI but on the aftermarket systems I've worked with the MAP line is primarily used to sense load and vary the ignition timing to suit (retard on low vac, advance on high)

K I will check fuel pressures. I'll head to autozone to rent the tool.

I never thought to mention but I did add a bottle of SeaFoam injector cleaning to the tank of gas...the bottle was for 12-20 gals...so I just poured in all of it. The bottle directions said it was ok...did it possibly dilute my fuel?? That even possible with those injector cleaners?

Quote from: wildgoody on June 12, 2011, 09:30:02 AM

I don't know what the manual says to do to check it, but somehow you are still getting a lean condition, because when you pull
the MAP vacuum line it tells the ECM more fuel, and your truck runs better

Good work so far
Wild

Are you sure about that?  It seems to be the reverse of the what I would expect.

A high vacuum on the MAP sensor would indicate a closed throttle, and as the throttle opens the vacuum decreases (gets closer to atmospheric pressure) - I'm not sure about the Samurai EFI but on the aftermarket systems I've worked with the MAP line is primarily used to sense load and vary the ignition timing to suit (retard on low vac, advance on high)

Ya, and you just said the same thing I did.

If you pull the vacuum line from the MAP is reads atmospheric pressure, similar to WOT 

K I will check fuel pressures. I'll head to autozone to rent the tool.

I never thought to mention but I did add a bottle of SeaFoam injector cleaning to the tank of gas...the bottle was for 12-20 gals...so I just poured in all of it. The bottle directions said it was ok...did it possibly dilute my fuel?? That even possible with those injector cleaners?

I don't think that Seafoam would cause the problem, but if the tank was full of gunk, it may of sent it to the
fuel filter or be clogging the sock on the fuel pump in the tank.

Pressure will tell you if that is the problem, but changing the filter is never a bad idea

Has the TPS been ruled out? I can't really adjust it to spec because my throttle lever stop screw is not in use at it's current setting...I forgot about the TPS...before I had a TPS adjustment CEL...I adjusted it with the ohm meter but without the .012 feeler and the CEL went away.

The fuel pressure test kit is quite large...I'm about to read how then test it

Thank you for all of your input!!!

I don't think it's ruled out, but the truck runs good when it gets enriched
so I think it's OK, what year is the truck again ? 

1990

Ya, and you just said the same thing I did.

If you pull the vacuum line from the MAP is reads atmospheric pressure, similar to WOT 

Aahh - pull the vacuum line = disconnect it, not pull a vaccum on it - my bad.

I'll have to see my options before doing the fuel pressure test. None of the adaptors in the kit will work...there is a T splice but not sure if cutting my hose is the way to go without a replacement hose...I'll go look around the parts store and see if there is a t made for this purpose

All you need is a double barb fitting and 2 clamps to put it back to 1 piece,
been running mine like that for well over 5 years now

Cool - picked up 3/8 barbs and clamps! I'll break it down tomorrow and see if we're measuring up to specs