P38A 1996 4.6 Auto HSE. driver side bags not inflating after valve block rebuild.

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Blant15

Member
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Hi All,

I've searched the forums and can't find anything posts that quite match up to the symptoms I'm having.

I just rebuild my valve block and compressor with the XR8 rebuild kits. Spent a full day rebuilding everything following PaulP38As guide for the valve block and XR8s guide for the compressor.

After refitting everything this morning I'm currently in this situation:
  • Both left side air bags seem to inflate and deflate through all the height settings as they should.
  • The front right bag only inflates to the standard ride height and no more.
  • The back right bag won't inflate at all and this corner is just sat on the bump stop.
  • After 5-10 minutes, I get a soft EAS fault. This is presumably because of the difference in sensor readings between all corners?

I removed the valve block to check my assembly work and unsurprisingly found when I pulled the line for the back right bag, there was no pressure in the line at all.
After removing the valve block I checked and confirmed the back right solenoid stem base o-ring was ok and then swapped the solenoids for the front left and back right and tested again. This changed nothing.

I've leaked tested, all the valve block collet ports. No issues there. I've removed the exhaust filter and confirmed air isn't passing on the diaphragm when the compressor is running.

It appears to me like the back right solenoid just isn't firing. Is this a driver pack issue? I've access to a nanocom unit that I can use to check the EAS fault code tomorrow.

I've been researching this issue for most of today and don't seem to be any further along. Is there something obvious I'm missing?

Thanks in advance!
 
First make sure you have plenty of air in the system. Assuming the ECU is feeding 12V to each driver pack input, there's two likely causes.

1) Bad contact in the connector between the driver pack & solenouds. Solution is to de-pin one socket at a time & gently squeeze the contact. I generally use a spare pressure scitch contact to check them. Several will be loose !!

2) Bad connection or dry joint on the wires entering the driver pack under the potting compound. I have one just like this, where the solenoid can be activated by wriggling the wire. Compound is a PITA to remove. :mad:

BTW, if you're swapping solenoids around to test things, make sure you know where they should go. Otherwise it will never behave properly afterwards.
 
pwood999 said:
First make sure you have plenty of air in the system. Assuming the ECU is feeding 12V to each driver pack input, there's two likely causes.

1) Bad contact in the connector between the driver pack & solenouds. Solution is to de-pin one socket at a time & gently squeeze the contact. I generally use a spare pressure scitch contact to check them. Several will be loose !!

2) Bad connection or dry joint on the wires entering the driver pack under the potting compound. I have one just like this, where the solenoid can be activated by wriggling the wire. Compound is a PITA to remove. :mad:

BTW, if you're swapping solenoids around to test things, make sure you know where they should go. Otherwise it will never behave properly afterwards.
Click to expand...
+1 to the connectors. Also double check you have the solenoids on in there correct positions.
 
Thanks for the replies so far. You have given me a few things to check.

I'm aware of the differences between the air bags solenoids and the diaphragm and exhaust solenoids for example. I labeled up all the solenoid with their original positions before I started the valve block rebuild. Would I be right in saying it shouldn't matter if I swap the air bags solenoids back as they should be identical anyway?
 
Solenoids must be in their correct positions. You can move them to check if there's a solenoid or stuck valve (never seen this), but they need to be in the correct position or the ECU will get confused. Remember when the ECU activates a corner valve, it expects the height to change or logs a fault.

Also add your Town name to your profile. Others with knowledge might be close by.
 
Just for clarification, Ive only swapped the solenoid tubes and bases. Not the actual coil caps. That makes sense why you can't swap the coil caps round.
 
When you did the o-rings, did you feel the "springyness" of the valve. If they move cleanly within the tube then they are not sticking, so should simply work. If sticky, check the tubes are clean inside !!

Easiest way to test things is with 12V feed directly to main connector on the front of the EAS housing. Nanocom can do it, but more fiddly, and involves the ECU.

Unplug C152, and then connect Ground & 12V to power the driver pack. Ground to Pins 10+11, and 12V to pins 12+13. Then apply 12V to pins 1, 2, 3, 4 for the corners. 12V to pins 5 & 6 for Intlet & Exhaust respectively. So to raise the rear apply 12V to pins 1, 2 & 5.

FYI, I made this to do all the manual testing !!

1718016758537.png
 
pwood999 said:
When you did the o-rings, did you feel the "springyness" of the valve. If they move cleanly within the tube then they are not sticking, so should simply work. If sticky, check the tubes are clean inside !!

Easiest way to test things is with 12V feed directly to main connector on the front of the EAS housing. Nanocom can do it, but more fiddly, and involves the ECU.

Unplug C152, and then connect Ground & 12V to power the driver pack. Ground to Pins 10+11, and 12V to pins 12+13. Then apply 12V to pins 1, 2, 3, 4 for the corners. 12V to pins 5 & 6 for Intlet & Exhaust respectively. So to raise the rear apply 12V to pins 1, 2 & 5.

FYI, I made this to do all the manual testing !!

View attachment 318974
Click to expand...
As I recall, all the plungers moved freely in the tubes.
I'll start by stripping the driver pack to solenoid plug and checking the contact between the pins. After that I'll try some manual testing with nanocom.

I'm now wondering if I could try swapping the coil caps to test if I can get the back right bag to inflate that way. Not sure if there is enough wire length however..
 
À daft question but did all the plungers go back back in the correct sense and not one upside down? It'll send air to the bag but won't allow it to hold air 🤔
 
Mark Piercy said:
À daft question but did all the plungers go back back in the correct sense and not one upside down? It'll send air to the bag but won't allow it to hold air 🤔
Click to expand...
I'm pretty confident all the plungers are the correct orientation but I can always double check when I remove the valve block again to check the driver pack plug.

I'm still a bit lost why the front right airbag won't fully inflate beyond approximately the standard ride height. Does the ECU or driver pack not let 2 bags on the same side go beyond a certain range of each other on the height sensors maybe?
 
Depends on the stored height settings in the ECU. You can read them with Nanocom.

If you do the manual test above with Inlet & both front bags they should both go to the same height. Once you get some air in them simply open just the FL & FR valves and the bags should equalize the air pressure. (exactly what the ECU does to balance the front when you stop at traffic lights with handbrake on & foot off the brake pedal.)
 
Blant15 said:
I'm pretty confident all the plungers are the correct orientation but I can always double check when I remove the valve block again to check the driver pack plug.

I'm still a bit lost why the front right airbag won't fully inflate beyond approximately the standard ride height. Does the ECU or driver pack not let 2 bags on the same side go beyond a certain range of each other on the height sensors maybe?
Click to expand...
The rears are supposed to inflate before the fronts, as one rear is not inflating, the ECU will limit the lift at the front.
 
I had a similar issue ages ago.
Using two trolley jacks, I raised the vehicle up a few inches before starting it. Turns out I had two bad ride height sensors. Jacking it up brought the sensors into a better operational range.
 
Update: thanks to Nanocom we were able to diagnose that I'd got the rear right and the front left solenoid coil caps mixed up... Apparently I wasn't as careful as I thought...swapped them back and the bags are all inflating as they should. Thanks again for everyone's replies and suggestions. Now on to the next task.

Can I ask another question about a separate EAS compressor issue here or should I start a new thread?
 
Blant15 said:
Update: thanks to Nanocom we were able to diagnose that I'd got the rear right and the front left solenoid coil caps mixed up... Apparently I wasn't as careful as I thought...swapped them back and the bags are all inflating as they should. Thanks again for everyone's replies and suggestions. Now on to the next task.

Can I ask another question about a separate EAS compressor issue here or should I start a new thread?
Click to expand...
It's always better to start a new thread for a separate problem.
 
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