B&S Vanguard 40hp EFI

[madmantrapper]

I am working a Wright 60" with this engine on it. My first question is can anyone explain how the ignition and fuel systems work? I don't work on many vanguards. The symptom is it will start every other turn of the switch. I know it sounds nuts. It will crank and crank and not start. Release the switch and hit it again and it will fire right up. Shut it off and try it again it will not start again, release the switch and hit it again, it will fire right up. Called Wright they said to change the fuses, as rediculous as that sounds, I tryed it, of course it didn't work.

Briggs says change the fuel pump, that didn't work either.

The guy working on it just came in a said it will fire up on the odd turn of the key with a shot of ether.

Any help would sure be appreciated.

There is no O2 sensor, how does the ECM know whats going on?

[bgsengine]

Might need a complex wiring diagram and/or a breakout box and familiarity with testing computer controls (Meaning being sure of your pinouts before connecting any meter leads) but I'd be wondering if it isn't seeing an intermittent grounding issue or a high resistance in a relay. Computer grounding that is.. You'd have to test if the injector(s) are firing (Noid light perhaps?) and if not, whether they are getting any signal from the ECM , and if they are, then possibly grounds (even a tiny bit of corrosion in a terminal connector might be enough) - may not be until the key is switched back to run position (Might even be a switch problem) that it gets a little jolt that completes a circuit which then allows things to operate normally. Lots of possibilities I can think of - Been through things like that often enough with cars when I worked at Ford dealer- Some troubleshooting involved a considerable number of steps and trouble-tree following In a couple cases it was traced down to just corroded metal under a screw that wasn't as tight as it should have been causing a ground resistance.

I'm SO glad I got out of the business when I did, as those electronic controls have been coming in to independent shops much more frequently (I've been asked a couple times to take a look, I said no thanks, unless they wanted to front me the money to buy the test and diagnostic tools that would be needed...LOL)

[bgsengine]

There is no O2 sensor, how does the ECM know whats going on?

Inference based on air flow rates & Temperature, and fuel injector duty cycle, among other inputs, can allow ECM to calculate what is needed... (Basically it'd be "Default" mode if it did have an O2 sensor, allowing engine to be run until it could be repaired)

[bluemower]

these can be tough. probably need to determine if this is an equipment problem or an engine problem. You did not provide any number for your engine, but the 61xxxx is the only model with 40hp.


1. use a code reader to see it there are any codes. If you do not have a code reader, download the computer program to your laptop. Will probably need help from Power Distributor technical support to get this set up. If there is a component failure on the engine, a code should appear.

2. another idea is to use your spark tester to verify you are getting sparks while the engine is cranking.

3. verify electrical power is delivered to the engine when the ign switch is turned to the "on" position. If power is delivered, perform the same check when the engine is cranking. Cranking RPM must be over 300 rpm. Maybe this will provide some clues. See what the battery voltage is while the engine is cranking. The comment about the starter fluid may be a clue there is not enough voltage available to operate all engine functions. Try connecting the battery ground directly to the engine. May sure all power is off when fooling around with electrical.

4. inspect the wire harness on the engine for evidence of damage or someone messing with wires. Look carefully at connectors. Check grounds for tightness and corrosion.

The service manual is located on the power portal. Section 3 has many suggestions. Ce 8182 is a dedicated manual for EFI. These can be difficult and time consuming especially for shops that do not normally service these.

[bluemower]

forgot to mention, somewhere, i recall a service bulletin that the o2 sensor is going away and the future engines are open loop.

[KE4AVB]

also there are three Big Block EFI service manuals in the Briggs downloads that might help. I checked the Briggs power portal no service bulletin found BGS but that don't mean one wasn't issued and then deleted.

Also note if attemptingto use the EFI test software you must have Win10 or later to use it but you be able to get the OBD codes without it.

[bluemower]

my mistake. the information concerning the elimination of the closed loop is in the 2023 update.

[KE4AVB]

Blue if you have that in PDF form PM me with it attached. PD and Briggs screw up my Power Portal account and now I only got a technician access. Actually the gave the account away to some business in Ohio.

[madmantrapper]

We ran diagnostics, no codes. It does get spark while cranking.

[KE4AVB]

I can't be of any help but it sounds a loose terminal/contact. I just haven't seen but two EFI engines and both of them were Kawasaki engines.

So be staying tune as to what you might find to be the problem.

POsting the model of the Wright mower might me to look for the wiring schematic on the mower's side of things.