EGR Test questions.

Chasing some smog issues led me to check my EGR on my 87xj.
If I manually press the EGR diaphragm at idle, the jeep will die. that's normal I believe.

If I manually put vacuum to the egr, diaphragm will not move/ not kill the jeep. Not normal I believe.

I can not get the jeep to SEND vaccum to the egr. I have tried rapidly opening and closing the throttle. No vacuum comes out of the black doohickey near the airbox (although vacuum is going into it). How can I check/fix that?

Note from DJ
This information may help
http://www.naxja.org/forum/showthread.php?t=993347
See post #3 by joe_peters
Please keep us posted as to your progress.

That's what i needed, thanks! By that procedure, my egr solenoid is not working. The transducer dookickey works when i unplug it. Wonder if i can clean it (solenoid)? My parts rig is an 88, and its egr solenoid looks a bit different than my 87s. Anyone know if they are interchangeable?

jrowell said:

Chasing some smog issues led me to check my EGR on my 87xj.
If I manually press the EGR diaphragm at idle, the jeep will die. that's normal I believe.

Click to expand...

Correct

jrowell said:

If I manually put vacuum to the egr, diaphragm will not move/ not kill the jeep. Not normal I believe.

Click to expand...

Also correct.

jrowell said:

I can not get the jeep to SEND vaccum to the egr. I have tried rapidly opening and closing the throttle. No vacuum comes out of the black doohickey near the airbox (although vacuum is going into it). How can I check/fix that?

Click to expand...

Sounds like you have two potential issues:

1) EGR Diaphragm failure. This is why you can't pull the EGR open by applying vacuum.

2) Potential EGR line/solenoid failure. Check the line from the EGR solenoid by blowing through it, air should move freely (it is a 1/8" ID, so bear that in mind.) It may be blown out with a bit of carburettor cleaner if you suspect a collection of oil in the line. Also, a bit of 18AWG or 16AWG copper wire, solid, stripped, and the end filed or sanded round, may be gently pushed through the line to clear it out.

The solenoid may be tested by pulling a vacuum on the engine side of it and applying 12VDC to the solenoid terminals, and checking vacuum at the EGR valve line. (The solenoid is that black dingus next to the airbox.)

At least you know you don't have to clean the EGR passages, but I'd recommend doing so while you've got the thing off to replace it. A small, flat screwdriver and a Shop-Vac will work neatly, it's what I usually use.

The screws are a Torx head, about a T35 or T40, I believe. The threads are 5/16"-18, so you can replace them - but I still recommend a socket head, since you don't have a lot of space there for an external wrench.

jrowell said:

That's what i needed, thanks! By that procedure, my egr solenoid is not working. The transducer dookickey works when i unplug it. Wonder if i can clean it (solenoid)? My parts rig is an 88, and its egr solenoid looks a bit different than my 87s. Anyone know if they are interchangeable?

Click to expand...

If the electrical connection is the same, it should be.

And, it's not a matter of cleaning - usually what happens is that the solenoid windings fail, and the part just wants replacing.

I think I'm calling the parts by the wrong name. I was calling ether black dookickey by the airbox the transducer. By reading your post, that is the solenoid. When i unplug the electrical, it sends vacuum to the egr. I think that rules it out. The actual egr piece on the manifold does not function when vacuum is applied, although i can manually press it and kill the engine. Is this piece interchangeable with one from an 88? They look pretty close.

It's been a long time since I dealt with an 87 EGR, but it's important to note that there are two designs of EGR possible. The first is a two part EGR with a separate transducer, and a simple vacuum diaphragm valve. This is what you will always find in an 88, I think. You can test the EGR portion with vacuum, and if it does not operate, it's bad.

However, the original one-piece EGR found on the 87 will NOT ever operate on vacuum alone, because it has a back-pressure valve built in (which the later transducer takes over). It will always leak vacuum, and if you test it with vacuum you may end up throwing a good one away.

It sounds as if you have the 2 part valve, and this one indeed can be vacuum tested, but I throw the above in just in case someone consults this subject later.

Matthew Currie said:

It's been a long time since I dealt with an 87 EGR, but it's important to note that there are two designs of EGR possible. The first is a two part EGR with a separate transducer, and a simple vacuum diaphragm valve. This is what you will always find in an 88, I think. You can test the EGR portion with vacuum, and if it does not operate, it's bad.

However, the original one-piece EGR found on the 87 will NOT ever operate on vacuum alone, because it has a back-pressure valve built in (which the later transducer takes over). It will always leak vacuum, and if you test it with vacuum you may end up throwing a good one away.

It sounds as if you have the 2 part valve, and this one indeed can be vacuum tested, but I throw the above in just in case someone consults this subject later.

Click to expand...

So, how do you test one from an 87?

this is Mine from my 87. And below is the one from my 88. It does have another port...

jrowell said:

So, how do you test one from an 87?

Click to expand...

That's a good question, and one I never found an answer for. As far as I know, the only way you can know it's working is by trying to duplicate the conditions under which it operates, and since it never seems to operate at idle, one is kind of stuck here. Of course if it sticks open, you'll know, but other than emissions results, I don't know if there's any way to tell easily if it's not working. On my 87 the exhaust tube rotted out, and I blocked it off, never noticing any change.

Note from DJ
Old style EGR System
Some of this information pertains to a carbureted engine but there are a lot of links regarding EGR systems.
http://home.sprynet.com/~dale02/egrvalve.htm
Keep us posted as to your progress.

djgrayxj said:

Note from DJ
Old style EGR System
Some of this information pertains to a carbureted engine but there are a lot of links regarding EGR systems.
http://home.sprynet.com/~dale02/egrvalve.htm
Keep us posted as to your progress.

Click to expand...

I don't see, however, that it covers the rather unique system of the old style XJ EGR. I have actually cut one open, and inside you will find that there is a metal plate that covers a hole in the diaphragm. A certain level of exhaust back pressure must be reached before that plate closes the hole. If you do not have the right combination of back pressure and vacuum from the solenoid, it is designed to leak.

I never found a reliable way to test one sitting still, and I suspect the only way to be sure it's working is by testing NOX emissions.

The later type, with a separate transducer, is much easier to test, since its diaphragm is normal. By the way, I did run into one instance where this type wore slightly off center, and hung open. You can reach in and tickle the diaphragm and make it snap shut.

If I swap it out with the 2 piece style that has the transducer will it still pass CA smog? Rock Auto only shows the 2 piece option for an 87... although they show the single piece like mine for an 88...

As long as the system is complete/functioning I do not see why it matters whether you have the UFO or not.

I doubt any smog guy would know the difference.

That, and with both parts looking very old, they probably wont give it a second glance.

jrowell said:

If I swap it out with the 2 piece style that has the transducer will it still pass CA smog? Rock Auto only shows the 2 piece option for an 87... although they show the single piece like mine for an 88...

Click to expand...

I've never been quite sure what the policy on these was, but I think perhaps that the one piece was routinely replaced in service by the two piece. Whatever the case, I would, if possible, use the two piece as a replacement, if only because it is possible to test this one with a simple vacuum test. I don't think there was any functional difference in operation.