Healthy ignition timing & fueling = orange/brown plugs

[fenns7]

As i was undertaking a plug and wire service thought I'd take some photos of the old plugs. I was surprised to see the oranage/brown colour of the insulators but remembered I had used an STP fuel additive to ensure the 4 hole injectors I'd fitted 3-4 years prior were as clean as possible.


Here are the plugs in order (no.1 cylinder to the right):





and from other side:






Close up both sides of no. 3:










Comparison of new Champion plug vs. old - note slight erosion of electrode.
*these plugs are maybe 3 years old (15k miles?) and gaps had been set at correct 0.35" and some had increased to 0.45" - 0.50":

 

[RCP Phx]

They don't look bad, what part# on the injectors? You might be a little "fat"!

 

[RCP Phx]

BTW, the '96 is a "bastard" year do you have OBD I or OBD II electronics?

 

[sandfreestyle]

Aside from the gap looking to be growing, they really don't look bad. Not great, but still usable if needed.

 

[fenns7]

BTW, the '96 is a "bastard" year do you have OBD I or OBD II electronics?

Oh yes, and don't I know it :looney:

It's OBD I and no scanners seem to link up to it (excluding expensive dealer only devices) so I use the '3 turns of the ignition key' to read any codes)

 

[fenns7]

Aside from the gap looking to be growing, they really don't look bad. Not great, but still usable if needed.

I'm pretty sure the orangey/red hue is largely due to the fuel system cleaner - seen it evidenced eleswhere. I'll check the new ones in a few months and post photos She runs smoothly and idles well (should do after all the work I've done!) so looking for nice tan colour and no fouling next time.

 

[fenns7]

Aside from the gap looking to be growing, they really don't look bad. Not great, but still usable if needed.

As I got a dozen Champions for 50c each I've junked the old ones (here in UK XJ consumables are sold cheap because vendors see no market - they're getting rare - or v. expensive for same reason)

 

[fenns7]

They don't look bad, what part# on the injectors? You might be a little "fat"!

I am indeed a little 'fat' but that's down to age & absence of regular exercise


If I can find order details on new injectors I'll post here but know they're reconditioned items from a US vendor. Good deal & spedy service if I remember correctly.

 

[RCP Phx]

You definitely need to change the plugs more often. Are you running the correct plugs?

 

[fenns7]

They don't look bad, what part# on the injectors? You might be a little "fat"!

Injectors were bought off ebay - from dsm-99 - have worked flawlessly.

Can recommend seller & injectors for a 1996 XJ

 

[fenns7]

You definitely need to change the plugs more often. Are you running the correct plugs?

pretty sure I am: Champion RC12LYC

 

[RCP Phx]

The plugs are correct but you would need to know the part# for the injectors to really tell anything. I don't think is much of a issue by your plug readings and since you are limited on actual O2 readings I wouldn't worry about it.

 

[lawsoncl]

Jeep UPGRADE 87-98 Set of 6 BOSCH FUEL INJECTORS 24LB EV1 4 HOLE 4.0L

Renix and HO don't take the same injectors though?

 

[fenns7]

The plugs are correct but you would need to know the part# for the injectors to really tell anything. I don't think is much of a issue by your plug readings and since you are limited on actual O2 readings I wouldn't worry about it.

I've done some digging through 'the archives' and found this photo of the injectors I used. They're Chrysler # 5277739 the Bosch equivalent being # 0280155703 22.7lb/hr @ 43.5psi

 

[fenns7]

Renix and HO don't take the same injectors though?

Quite right - I've removed the link in that earlier post as it was dead anyway.

 

[fenns7]

The plugs are correct but you would need to know the part# for the injectors to really tell anything. I don't think is much of a issue by your plug readings and since you are limited on actual O2 readings I wouldn't worry about it.

Checking against the chart below maybe the flow rate is a touch lean for a '96 which runs ar 49psi?

 

[RCP Phx]

Possibly if your pressure is not correct, but that injector will flow more (see example) at 49psi.

 

[lawsoncl]

Possibly if your pressure is not correct, but that injector will flow more (see example) at 49psi.

The 703 are a good match. 22.7 @ 43-psi => 24.09 @ 49-psi.

The formula is SQRT(new_pressure/old_pressure) * old_flow_rate = new_flow_rate.

 

[fenns7]

:cheers: