Air injection System Off, Ports Open, GW runs fine

[Dave Jeeper]

I installed a Howell TBI system on my 89 G Wag with 95,000 miles. While removing the air injection system I found that the air pipe running behind the engine and down to the catalytic converter had a big hole in it from rubbing on the back of the engine. There was no way that I ever would have found the hole without removing the pipe.


Just some info for people to consider when restoring the original emissions system.

[tgreese]

Should not matter as long as the proper signals (manifold vacuum, ported vacuum) are connected to the devices that need them. Some have check valves or delay valves inline that change the signal. For example, I expect your vacuum reservoir has an internal check valve that holds the reservoir high when the vacuum is low, converting the vacuum signal to a power source.

[Bob Barry]

Thanks Bob, so two vac lines (from the check valves) would "t" together into a single line that normally then "t's" into the rear heater hose connection, correct? Thanks again!

Yes, I believe that's the factory routing, but double-check a schematic in case my memory is faulty.

[rang-a-stang]

That makes perfect sense. I did not drive with my air injection much; just usually a week at a time around smog time so I did not spend a lot of effort or brain power figuring it out.

[tgreese]

I lost the output hose from my pump to the check valves once and my engine would burble and backfire on deceleration.

The diverter valve was sometimes called the anti-backfire valve or burp valve, back in the day. From your description, it seems the check valves will admit air on deccelleration. Or maybe your check valves weren't sealing so well.

[rang-a-stang]

I lost the output hose from my pump to the check valves once and my engine would burble and backfire on deceleration.

[warmblood58]

The check-valves will eventually rust and leak if the AIR pump is not pushing air past them on a regular basis.

You can disconnect the vacuum hoses and plug them at the source, which should be the dual-CTO on the back of the intake, t'd into the rear heater hose connection. Splurge for the actual vacuum-caps to plug them.

Thanks Bob, so two vac lines (from the check valves) would "t" together into a single line that normally then "t's" into the rear heater hose connection, correct? Thanks again!

[Bob Barry]

The check-valves will eventually rust and leak if the AIR pump is not pushing air past them on a regular basis.

You can disconnect the vacuum hoses and plug them at the source, which should be the dual-CTO on the back of the intake, t'd into the rear heater hose connection. Splurge for the actual vacuum-caps to plug them.

[letank]

missed this one... as you do not have smog test... if the check valves are not blowing exhaust gas in the engine bay, remove the air pump, there might be some residual air popping from the check valve, so you can connect both check valve with their initial hoses, you may need a connector to join those large bore hoses

[warmblood58]

Question, I have been cleaning up the engine bay on my '88 GW, currently the injection pump is blowing air into the bay (all the hoses are removed from the check valves ) - GW runs fine but will be reinstalling hoses etc. Aside from the air from the spinning pump and open check valves, would would be the effect on the engine with an "open" air injection system? Where do the vac hoses that are on the two little metal cannisters (control valve) tie into? Thanks!