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Old 02-18-2009, 05:56 PM   #1
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91 jetta sparks on plugs only when turn key to on

I have a 91 jetta 1.8 FI. The fuel pump in the tank went out. While finding this out I ran the battery DEAD. Now when I turn key to on, I hear a (one)pop sound in the distributor.
With coil wire out of dist cap but resting very near the coil wire hole in cap, when key is turned to on, the pop noise is actually a spark (one only). Whith spark plug out, hooked to plug wire and resting on lifting hole on engine, it too sparks one time when turning key to on. When turning key to start, turning engine over, no spark at all. Also the fuel pump in front of tank used to come on for 1-2 seconds when key turned to on, now it does not but does when turning engine over. Has fuel flow at injector inlet however spark plug is dry as a bone. Anybody have a clue about these problems? Want to buy this one you can have it for what I paid. $700
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Old 02-18-2009, 08:56 PM   #2
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Re: 91 jetta sparks on plugs only when turn key to on

A spark when you turn the key on may be normal - but it should only flow to the plug wire whose terminal in the dist. cap is closest to the end of the rotor inside the cap. If you get a spark at the end of an ignition wire - it would make me think there was something conducting the spark inside the distributor that should NOT be. Like the inside of the cap or the rotor being wet or having an arc track. So pull the distributor car and rotor and inspect them under a strong light - for cracks or arching or moisture. The next step might be to try a new ignition control module. I see them costing as low as $30 odd, but some costing over $100. They might be available from a junkyard - if you can find one that has any Mk-II Jettas. And have the distributor cap off when you crank the engine, to make sure the rotor is turning. Also check to see if you are getting spark At the Ignition Coil. Is the timing belt intact?
I never knew if both fuel pumps turned on when I first turned the ignition key on, but certainly you should hear one of them run.
The plugs being dry might be normal; since it takes very little fuel to start an engine that has injectors. There is a little screw fitting in the small diameter tube at the end of the fuel rail facing toward the brakes. If you remove that little screw (metric 4mm dia. by about 6mm long, and probably having a 7 mm hex head) the fuel should squirt out; if the fuel pump had been on in the couple of hours. If you clamp put a 5/16" hose on that port, and connect it to a pressure gauge - the normal reading with just having turned the ign key on should be at least 40 psi. (If the car has been sitting it may take multiple operations of the ign. key On-off-on-off. to give the pressure time to build up.
And with the engine running I would expect the fuel pressure to be about 40 psi, varying from about 36-44 psi, depending on the vacuum in the intake manifold.
And of course: Be VERY careful working around gasoline fumes and spray.
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jetta, no spark, sell
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