a mystery
04-08-2015, 08:42 PM
#1
8th Gear
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Join Date: Dec 2007
Location: Newnan, Ga
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a mystery
I have an 84 Carrera Coupe with 55,000 miles and live in Georgia. I am having a strange no start problem. When it was cold this winter the car would not start. I tried it on several occasions with no luck. I changed out the DME relay and the fuel pump relay and still no luck. I figured it was a tired fuel pump.It lives in an unheated garage and since I don't drive it much in the winter,I just covered it and went on with life. Last Saturday I pulled off the cover and it started right up. I took it to a friends shop and everything checks out...fuel pressure is fine and we are stumped...any ideas....thanks in advance
04-09-2015, 10:27 AM
#3
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It's best to determine if this is a no spark or no fuel condition to really get a handle on what it will take to fix it. The DME relay sounds likely and can be "jumped" to force the fuel pump on. If you bought one of the non-porsche DME relays, they are known to be bad out of the box. So next time it doesn't start, get a helper, pull a spark plug wire, put a loose spark plug in the end of the cable, ground the outside to the metal of the engine and have the helper crank it over. If you have spark, you then have a fuel issue or vice\versa
04-09-2015, 05:03 PM
#4
Personally i'd figure out no spark vs no fuel
use alittle starting fluid under the airbox flap/valve - take off the filter and top spray inside the flap
then try and see if it starts, then you know no fuel
if it starts then check the fuel pump see if you hear it on on position, injectors sound ect.
double check your DME relay make sure its good.
tank. lines clogged, filter clogged.
then move on to no spark protocal.
ground a plug. see if you have spark
check distrubitor, coil, wires
ive noticed in these cars its usualyl the distributor or the fuel pump.
its pretty simple
use alittle starting fluid under the airbox flap/valve - take off the filter and top spray inside the flap
then try and see if it starts, then you know no fuel
if it starts then check the fuel pump see if you hear it on on position, injectors sound ect.
double check your DME relay make sure its good.
tank. lines clogged, filter clogged.
then move on to no spark protocal.
ground a plug. see if you have spark
check distrubitor, coil, wires
ive noticed in these cars its usualyl the distributor or the fuel pump.
its pretty simple
04-13-2015, 01:20 AM
#5
RL Technical Advisor
Hi,
Remember, the DME relay powers both the fuel pump & DME which means no fuel or spark if its not working correctly. At 55K, your fuel pump should be OK although the filters (engine compartment and in-tank) may need replacement.
Now,....QC on these relays (factory or aftermarket) is intermittent and I've replaced/sold/repaired one helluva lot of these things over the years. For that reason, I re-solder each & every one we sell/install so we have a good sense of reliability.
Naturally, I have to assume that your battery is in top shape and all of the battery connections and grounds have been cleaned so they are bright & shiny (this assures proper conductivity).
Remember, the DME relay powers both the fuel pump & DME which means no fuel or spark if its not working correctly. At 55K, your fuel pump should be OK although the filters (engine compartment and in-tank) may need replacement.
Now,....QC on these relays (factory or aftermarket) is intermittent and I've replaced/sold/repaired one helluva lot of these things over the years. For that reason, I re-solder each & every one we sell/install so we have a good sense of reliability.
Naturally, I have to assume that your battery is in top shape and all of the battery connections and grounds have been cleaned so they are bright & shiny (this assures proper conductivity).