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What to do with the Secondary Air Injection system (ACU engine)

 

Hello,
?
I'm troubleshooting a 1995 Rialta with ACU engine for a friend who just bought it.? There were monkeys in the engine bay: loose wires, disconnected vacuum hoses, SAI check valve cut out, radiator blower fans bypassed with a switch - a real mess.
In comparison to my old AAB, this engine has some extra complications, like the SAI system.? My question is this:? should I try to reconnect and repair the SAI, or should I rather do away with it.? Has anyone successfully removed that system? Will the engine run correctly without it?
Thanks for any suggestions,
?
Radek
 

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Hi Radek,
As far as I know, the secondary air injection system only operates for the first 60 or 90 seconds of a cold start. It pumps air into the exhaust flow to help the catalytic converter convert all the unburned fuel. As long as the system isn’t the source of exhaust or intake leaks, the van should run fine without it. See this samba thread for more info:?


Thank you,
Quinn

On Sep 15, 2024, at 8:44?PM, Radek <radek.radarski@...> wrote:

?
Hello,
?
I'm troubleshooting a 1995 Rialta with ACU engine for a friend who just bought it.? There were monkeys in the engine bay: loose wires, disconnected vacuum hoses, SAI check valve cut out, radiator blower fans bypassed with a switch - a real mess.
In comparison to my old AAB, this engine has some extra complications, like the SAI system.? My question is this:? should I try to reconnect and repair the SAI, or should I rather do away with it.? Has anyone successfully removed that system? Will the engine run correctly without it?
Thanks for any suggestions,
?
Radek
 

The SAI failed about 25 years ago, disconnected, passes Oregon sniffer rules. YMIV I suppose but looks optional…one less drag on the serpentine belt!

1995 Eurovan Camper Syncro
450000 miles and still For Sale

Cheers, jc
 

Thank you guys for the for confirmation and reinforcement. I saw the van again today and did some more troubleshooting (new air filter, new fuel pressure regulator, check spark plugs, try to make sense of the vacuum lines).? When I got to removing the SAI, it was already disabled (a small plate blocking the metal pipe to engine head).? So all that fiddling with vacuum lines and valves was unnecessary, the system was dead anyway.
?
So here is what I know at this point:
1. when the Fuel Pressure Regulator and the Atmospheric Pressure Sensor (in the ECU) vacuum line is connected, engine runs fine at first but eventually dies at idle.
2. it runs best with FPR and APS disconnected, the vacuum line open and sucking in air.
3. spark plugs are black and sooty.
4. oxygen sensor is probably dead, disconnecting it wouldn't make any difference.
?
When I see the van again in a few days, my plan is:
1. change the O2 sensor,
2. change the fuel filter,
3. test the idle valve (it is vibrating to the touch with the key on, but have somewhere an old one I can swap in),
4. test the EGR valve
Anything else? Thanks a lot for your help!
?
 

Sounds like a fuel pump issue. Sometimes when they fail, the flow rate slowly drops as they warm up. By disconnecting the FPR vacuum line, you are raising the fuel pressure at idle (spec is 36psi with vac connected, 43psi disconnected) to compensate for the reduced flow rate.
?
There's a procedure in the service manual to check the fuel pump flow rate (~500ml over 30s at 43psi) but a simpler test that you do is to hook up a fuel pressure gauge and see if the pressure starts to fall below 36psi at idle.
 

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Black and sooty spark plugs means you are not burning the gas…………
The reason can be weak spark, bad plugs, too much gas, timing, low compression, plug wires, ?

On Sep 22, 2024, at 10:02 AM, Herman via groups.io <h3ch4@...> wrote:

?
Sounds like a fuel pump issue. Sometimes when they fail, the flow rate slowly drops as they warm up. By disconnecting the FPR vacuum line, you are raising the fuel pressure at idle (spec is 36psi with vac connected, 43psi disconnected) to compensate for the reduced flow rate.
?
There's a procedure in the service manual to check the fuel pump flow rate (~500ml over 30s at 43psi) but a simpler test that you do is to hook up a fuel pressure gauge and see if the pressure starts to fall below 36psi at idle.
 

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