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Discussion Starter · #1 ·
1988 RC 318 TBI
I'm getting vacuum to the EGR all the time, even with the engine cold. It runs ok with the vacuum line disconnected, but as soon as it's hooked up, it starts running rough. I'm assuming that there shouldn't be any vacuum when the engine is cold. The coolant sender reads about 13500 ohms when cold, so it appears to be ok. The 88 FSM isn't really clear on how to test the EGR solenoid. Am I correct in assuming that the solenoid should only allow vacuum to the EGR when the coolant temperature sender is warm enough to complete the circuit ? Is the EGR solenoid supposed to be normally closed or normally open with the ignition off? Any suggestions for testing it?
Even with the engine at operating temperature, I can’t hook up the vacuum line without it wanting to stall. Does this mean that the back pressure transducer is screwed as well?
Thanks,
K.C.

 

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no the solenoid is / l have the part number for the new one at work / l,ll post it MON afternoon / l just went thru the same thing with a 89 RC
 

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heres the dealer # 1-05227635 and its about $ 35 bucks / you mite be able to get it a parts store also if they can cross the number over
 

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Discussion Starter · #5 ·
BartonsBest said:
Another option is to leave the vacuum hose off. The egr should only open at low load cruise conditions. Of course it won't pass emissions testing if it is left disconnected.

Good Luck!
Bruce
Bogger 35 thanks for the number.

BartonsBest...... that's the part that I don't understand. I took this thing through the "Air Care" emissions test with the hose disconnected and it passed with flying colours. They didn't do an underhood inspection, just used a mirror to make sure the cat was there. NOX was 520ppm with max allowable 1129ppm and average vehicle passing reading is 385. It was above normal, but I had room to take another RC through there with me! It's been a year since I went through and thought I might not be so lucky this time... Thought I should fix it cause the readings didn't seem logical.
 

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Hi K.C.

This info may or may not help you as I have an Edelbrock intake, but with my Edelbrock intake, Napa parts "Standard Professional Quality Automotive Parts" numbers PVS20 and PVS11 will replace the computer controlled vacuum switches for EGR, air pump, distributor, hot air door, and fuel vapor purge canister operations. These replacements will screw directly into the Edelbrock intake, but they will be a tight fit.

I don't know first hand if they will work with the stock intake, and sorry but I don’t know how to test the stock stuff as the previous owner had already replaced my computer, EFI, and intake with a carb! I would think however that these switches may screw into the water jackets on an OEM intake, but you will have to check on this yourself.

These switches will open or close at the correct temperatures as well, I made sure of that. These part numbers took me a bit of time to research, but they work well as I not only passed smog in NV just fine, but they mimic the computer controlled switching operations perfectly.

You are correct in that the EGR should not get vacuum when in cold operation or at WOT. This is done using the PVS11 switch which has two ports, and is normally cold closed being feed off of the carburetor ported line (none @ idle or WOT). You should also know that purge canister and EGR should be tied together, as when the EGR is pulled, so should the purge canister. That is to say no purging fuel canister vapors into a cold engine or at WOT etc.

The second switch I mentioned (PVS20) uses vacuum from the carb to operate the air pump, which should be exhaust manifolds cold, and downstream to catalytic converter when warm. Seems like I have the distributor and hot air door from the exhaust manifolds hooked into these switches as well, but I am too partied out now to recall all the details of the install. If you would like more info, let me know, and I will chime in tomorrow night and give more details on how I connected these ported vacuum switches.

Good luck and good night,
 

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he,s running the EFI and the part he needs to replace is a two second job and under 50 bucks / what you did to get yer EFI truck to pass with CARB is very good info / you should post it and then let a MOD read it to see if it can go in the HOWTO or F&Q section
 
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