Laser EFI questions....T Rex or Tony B?

I have a harness that seems to have a different color code then the manual I have mentions. I need to know---the 2 brown wires on the EFI harness---air temp sensor correct? I believe the manual said black. Also there are 2 long beige wires with black stripes---Is that for the temp enrichment of the ECU when the motor is cold? Assuming so . Just need verified. Also By leaving the 2 beige wires open circuit how much is the box enriched ( 10%???) and through what rpm range---whole range?? Lastly my harness has red and black wires for the fuel pump. I think the manual said red w/ purple and red or something. Do all of the Laser ECU's reduce fuel pump voltage at low rpms ? I am running a Bosche pump and 39psi reg off a 260 and eliminating the sump setup. I thought about running a BG relay and running the relay off the purple key switched wire as I have all my 260 motors. Comments?
Any advantage to any other ECU's--A48 for instance. How does it compare to the A17 or whatever recurved Laser box one might run?
Thanks for any info. Tony your check is in the mail and I have a few other items I'll be ordering. Thanks Steve

Steve,

For the air temp sensor, there is one brown wire @ pin 12, one black to ground and pin 16. Disconnecting the sensor results in +10% fuel delivery, shorting the circuit results in -10%. This is at all rpm ranges.

The 2 long tan/black wires go to the head temp sensor. an open circuit can increase fuel delivery up to 40%, but not at W.O.T.

I think that all laser ECU's have a fuel pump driver circuit that adds positive voltage through red/purple wire to the negative terminal below 2000 rpm to reduce pump speed.

I may call you on Mon about this one. I am certain that my harness has 2 brown wired for the Air Temp. I'll use the voltmeter and check cont. to the pins--#12 and #16 for that circuit. Also is there a way to bypass the water temp circuit? I assume it uses a Thermistor that changes value when it warms. I assume I can insert a fixed value resistor in the circuit. Also I have only the red and black wires for the pump. Which pin are they in the harness and should I run the pump direct or use the reduced bias voltage from the harness?? Thanks

Steve,

In place of the head temp sensor, I use a 270 ohm resistor to simulate normal temp. I wire this up to a dash switch, opening the circuit to activate cold start enrichment.

Just wire your pump like your 260 motor. That's what I do.

One of the harness leads to the air temp sensor should be to ground. Both leads of the air temp sensor are brown.

The red wire for the fuel pump is #6, the red/purple should be #2.

Tony , for fuel enrichment why don't you just run the yel / blk from the Merc harness to the yel red on the ECU harness and use the key push in ? From Merc they come with the yel / red on the ECU hooked to the yel/ red from theMerc harness to enrichen the ECU during cranking. We hook the yel blk up instead so that you push the key in to choke the motor. I am assuming that the water temp enrichment is not needed if you just use the key enrichment switch. I think its like 20%. I'll run a 270 in the water temp sender then. Thanks. This also makes the ECU easier to dial in because of less variables , looks like. STeve

I have a '89 200 XRi. I have had a lot of the same questions, and as I look on, I find this all to be very helpful. Mine started acting up at the end of the summer:

I tried to start it normally, it cranked, and cranked, and cranked.
No fire. nothing. Plugs didn't seem wet at all.
Not enough voltage?? I replaced the battery. WOW! cranked much faster, but still NO FIRE!
I was finally able to start it by adding some start fluid to one cylinder. (I know, i know, bad, bad, save the lecture)
Someone told me that I could richen the mix by unplugging the ambient air temp sensor (the one in the intake.) It worked, I could start it with the sensor unplugged, then plug it back in after it warmed up.

So, what happened? Did one of the sensors fail? Once it's running, the WOT is fine. This motor has always lean-sneezed a little bit at idle.

Someone once told me the resistor/sensor by-pass trick, but I think they were bypassing the air temp sensor instead of the head temp.

How do I test the sensors? Nobody has been able to give me some typical resistance values at given temps. Does anyone have an ohmmeter handy? I measaured them before I stored it for winter, and one sensor was 4K, the other was 12K (50 degrees outside maybe?), but I don't remember which value was which.

Steve, your wire colors are the same as mine, from what I remember.

-Chad

Steve,

I guess that would work too. Interupting the head temp circuit goes 40% rich at idle though, that will light at any temperature.

Pyro, I've got a switch on the air temp sensor too. It's cheap insurance when cruising with a Mod-VP ECU. They're very lean between 4500-6000 rpm. No problem if you accelerate through that range, but linger there for long and POP! Flip the switch and you're safe.

@ 50 degrees your air temp sensor should be about 12 K and the head temp should be about 2 K. Make sure that you've got a good ground on the sensors. The TPI is in circuit with the head temp sensor. Check that for improper adjustment, or a flat spot.

Tony

Be sho ya grounds are good...if ya air box ain't grounded good, it will drive ya nuts...injectors will fire sumtimes, and very weak sumtimes...sumtimes it won't even crank at all...Don't think ya bolts are enuf to ground everthang, cuz it aint...run a #10 wire from the bolt where the neg battery cable botls to the block, to the middle of the air box in which the injectors are in...also make sure ya ECU iz double grounded...halfassed grounds have killed more ECU's than anything...REX:cool:

Thanks, Tony, for the resistance values and advice. This spring, I will wire up a couple of bypass switches, I also plan to pull oil injection at that time.

Thanks, T-Rex, I'll check those naughty ground connections.

-Chad

I revived this old thread to ask for more EFI advice. Tony, you gave me some typical resistance values for 50 degrees. Well, it's 50 degrees outside today, and here's what I got:

Ambient / Intake temp sensor: 16.4 K
Head temp sensor: 1.9 K

Ambient sounds high, head sounds too low. Maybe that sensor is bad????

T-Rex, regarding the grounds... Where does the wire in the photo go? It looks like it broke off from a screw tab somewhere.

I want to hook up the "push key" switch for cold start enrichment. Is this switch normally open? Which wires does it hook up to? Do I have to take the control box apart? I know how to wire up a normally-closed relay to disconnect one of the sensors.

Any ideas???

-Chad

Make sho the ecu iz grounded...there should be a ground connected to a screw like tha one in tha pic...If there iz nun, put a term on the wire in the pic and place it under screw in the pic, in the ecu...The yellow wit a black trace iz the enrichment wire...sum ecu enrich when ya turn the key, and sum don't...if there iz a yellow/black wire un hooked, hook it up, cuz all the switch keys have the push enrichment feature...REX:cool:

ground wire . From the looks of it , someone may have run it to the trim solenoids if they mounted them in front of the ECU. If there is no ground running from the big ground on the starter, then run that wire back to the starter to be sure the ECU is grounded.
The yellow wire with red stripe coming from the ECU is the enrichment wire. Many motors have it hooked to the starter solenoid so that the motor richens as you crank. Most people prefer to hook the yellow with black stripe in the motor harness that comes from the key switch to the yellow with red in the ECU harness. Hopefully that is a clear enough expanation in a bit more detail . TRex mentioned the same thing.

I prefer 300minimum---1K ohm max in the head temp sender if you are running just a resistor. It gives a leaner bottom end with a smaller ohm resistor 0---3,000 rpm is the affected range. Depends on boat weight etc. I needed help with an older wiring code and I learned a bunch from this thread myself.
Have a great season!!!!! Steve

So, does it sound like one of the sensors is bad? Why doesn't this damned motor start with all the sensors plugged in? I shouldn't have to wire up bypass switches. It worked fine at the beginning of last season, then one day, it wouldn't start without adding fuel to a cylinder, or unplugging the ambient sensor.

As far as the wire goes, maybe someone can look under their hood and check for me. It wasn't for any solenoid. This motor is un-touched except for addition of solid mounts and removal of thermostat. Everything else is stock.

This is regarding my no-cold-start problem--

I may have found a possible cause-- For starters, my camera battery is shot, so I can't take a picture to show you, but here goes:
The two trim/tilt solenoids on the back of the powerhead have a big red supply wire feeding both of them. The bottom solenoid has a second red wire that goes to a fuse holder. That red wire looks to be broken from the connector!!! What function does the little module in the cowl pan perform? That appears to be where the red wire goes.

At approx. 65* F, air temp sensor is 12.8 K, and head temp sensor is 1.6K.
Does this sound right?

-Chad