Here are the conditions: 1) Drove car previous night, no problems 2) Car has recent battery replacement 3) Upon turning key to "on" air pump starts up (not normal, air pump should fire up upon engine starting, not before) 4) Car cranks, but will not start (btw 1997 5.2 Motronic) Here is what I did: 1) Shut off car at main battery switch, turned back on, and symptons remain. 2) Removed relay for air pump and inspected...reinstalled...symptons remain. 3) Removed and examined fuel pump fuse, air pump fuse and a few others...all fine. Reinstalled and turned on ignition, and now air pump does not come on, and now car starts normally. Any guesses what the cause might be? Bad air pump relay? Just a confusing set of circumstances for my limited diagnositic skills. I hate to wait for this to rear it's ugly head again, and away from the convenience of my garage and tools.
I'm glad you figured it out. I had the car out last night and plan to take her for a drive tomorrow, enjoy ever chance of driving her until the snow falls.
Guesses? I'd guess a floating/bad ground issue. I'd be curious if there was a way to figure out how to get the air pump tricked back on again with the engine off.
BING! I think you're on to something. I would start at the battery, clean and secure ALL the ground connections and check/clean any other fuses, relays and any other connections you can easily access. Check the alternator output (should be between 13.5 and 14.5 volts).
Voltage is 12.89 engine off, and 14.59 engine running. Never had any electrical issues with car. Lights are bright, accessories all work perfectly.
What does the circuit diagram look like for the air pump? Or more importantly, can you tell (by any means) if the air pump "on" signal is from a ground being connected...or from +12v power being connected to it?
I will have to look at the diagram...give me a minute. I just checked, it is switched on from +12...it shows the neg (black) wire going to a ground in the diagram. I am thinking more of a faulty (sticky) relay. No one agrees?
Some relays or circuits always have power, and a ground then activates them. Other circuits always have a ground, so supplying power activates them. Anyway, I'd just be curious to know if you've got pins in some engine-bay Amp connector that are shorting together...or if you've got a chassis-wide floating ground issue. Neither is a serious problem...just takes some trouble-shooting.
Maybe, but the relay is designed to have no power when the ignition key was off...to explain why your air pump wasn't still on when you turned off the car last night? I mean, you turned on the key and the air pump came on before the engine started, so your theory is that the relay was stuck all night prior to that?
Here is a thought as to a cause for a worn/bad relay in this case. The circuit was originally designed with a 15 amp fuse. The relay also says on it "12v 2 x 15 amp" or something like that. See here: http://67.129.153.73/CGv2Production/Pictures/Volvo%20J-Pegs%5C0332015006.jpg A common problem on 355's is for the fuse to blow, causing a "check engine" light to illuminate. The FNA fix was to tell dealers to replace the 15 amp fuse with a 20 amp fuse. My car has this 20 amp fuse. But, the question I am wondering, is the relay a 15 amp relay, and thus undersize for the circuit? Which may cause it to wear prematurely? Or is this a dual terminal relay, so 2 x 15 amp means it can handle 30 amps? But I am thinking that it is only using one leg of the relay to power the air pump, hence 15 amps max. I am not an EE so don't know the answer.
The current rating for that ...006 relay is 30A into the #30 terminal with 15A flowing out each #87b terminal. The thing with going to a bigger fuse can be related to current-vs-time with the electric air pump motor. At start-up there is a very high (but brief) current inrush (because the motor is not spinning yet, it is not generating any back EMF) that might blow the 15A fuse even though the steady state motor current is less than 15A. Does this mean that they are breaking the rules with regard to the relay's 15A current rating in each leg? -- maybe a bit. Could an internally stuck ...006 relay cause your symptom? -- seems possible, but if the thing that actuates the ...006 relay is stuck/malfunctioning you would get the same symptom (i.e., the fault could be some upstream gremlin telling the ..006 relay to close with just the key "on"). Feel free to shoot me a scan of the schematic if you'd like me to cast an eyeball over it D.
Thanks Steve! A problem I just found is the WSM I have only has the wiring schematic for the 95 MY 355. And not the later cars. Strange, since it has the seperate sections for the later cars related to brakes, clutch and engine management. I did note in the 95 diagram that one leg of that relay powers the air pump and the other leg powers "solenoid valve for RH cylinder bank secondary air". The WSM description of the 5.2 motronic does mention that the air pump and secondary air solenoid valve are in parallel on that relay, which sounds the same as the early 355's.
Assuming this relay did stick in the "on" position, energizing both the air pump and valve, I wonder if this would have caused the motronic to detect a problem and cut spart and fuel and prevent the car from starting, as happened this morning?
M5.2 would throw an error code if it halted fuel or spark due to seeing a problem, so unless you saw a CEL, I'd think that the problem would be something else.
Unfortunately, that's sort of "situation normal" IME (the WSM only covers the initial type of a model), and there's probably a separate "US-version 355 2.7 Motronic Wiring Diagram Book" out there. I'm guessing that it's more (or further upstream) than just a relay sticking problem because usually the +12V power to run things associated with the injection systems (fuel pumps, emission garb, etc.) is only supplied if the starter motor is actually cranking or if the engine is actually running -- i.e., if some problem is making this +12V available with just the key "on", even though the engine isn't cranking nor running, the passive componets (like a closed thermoswitch indicating "cold") will still be working and this would cause the ..006 relay to close. If it happens again, unplug the ...006 relay (while you have the key "on") and then just touch/untouch the male relay tabs into the female relay sockets and see if you can "feel" the relay internals clicking close/open as you make and break contact (indicating that the relay itsef is OK) or if it seems dead (relay stuck). Or alternatively, unplug the ...006 relay when you have the problem occurring, and measure the voltage between the 85 female socket and the 86 female socket -- +12V being present would maybe confirm some sort of an upstream problem.
Thanks Steve, I will keep you post for reference if this recurs and try your diagnostic tips. As always, I greatly appreciate everyone's assistance. Dave
The WSM says that the motronic needs to see the error at least two cycles before it will throw a "check engine" light. I recall my technician saying it is actually three times, regardless, this has only occurred once, so unlikely to have thrown a light, though a code may be stored in memory.
BTW Steve, I did switch the ignition on/off several times while I as messing with the relays last evening and checking for function, the only one that I could feel working was the "key activation relay"....not the air pump. Only thing is I cannot recall if this was before or after I fiddled with the relay and fuses and got the air pump to shut off. I think it was after.....
