Edited discription. We have a 93 939 that started being cold natured. Even on hot days it would die after you first started it. After it warmed up it was ok. Within a couple of days, when it was being driven down the highway at 70 mph, it died like it ran out of gas. It is not getting power to the spark plugs or to the fuel pump. Does anyone know if this is related to the computer. Or have any idea what it could be.

 

It could certainly be related to the computer but that is usually the last resort as a new computer is very expensive. Try checking both the fuel pump relay and the main relay. Both are located in the underhood fuse box right next to each other. The fuel pump relay would not cause loss of spark but only power to the fuel pump. The main relay supplies power to most everything including the fuel pump relay.

 

Specifically, which is the main relay and which is the fuel pump relay? The labelling in the fuse box is vague. There is a combination fuse box/relay box by the battery, and also one by the drivers side fender well. Which one would contain these? We do not have the owner's manual on this vehicle.

 

Both relays would be in the box by the batttery. There should be a label on the top or underside of cover that identifies each fuse and relay. Will post a picture of wiring diagram to maybe help. Both relays should click once when trying to start vehicle. Do you have a 12 volt test light? If so then remove the fuel pump relay and you will see four electrical pins that the relay plugs into. You should have power (test light will illuminate) at two of the four electrical pins. I two have power then main relay should be ok. If only one has power then possible that main relay is faulty.

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Picts came out a little dark so tried again out in the sun. Hopefully will come out better. Included wiring diagram of relays and where they get power from etc. if that will help.

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I am not sure my last comment worked so here I go again. Does the 93 929 have an engine that has valves hitting the pistons if the timing belt breaks? I have the car at a mechanic and he said he was told that the v6 engine in this car has that type of engine in it. Again the car was cruising down the interstate and acted like it ran out of gas. When I tried to restart it, it sounded just like it always did. No loud noise or turning over too freely. He said he is sure the timing belt has broken, but what does that have to do with no power to the fuel pump? Thank you for your help.

 

The type of engine where valves hit the piston is called a 'non clearance' engine. Your engine is not. If your timing belt breaks then you should be able to install new belt with no valve damage. Have seen many, many 929 and MPV come in with belt broken and no engine damage. Yes it will crank differently if belt is broken. If still sounds the same cranking as before then probably is not. How do you know fuel pump does not have power? And are you sure there is not spark to the plugs?

 

When the key is on, the fuel pump does not run so I metered and sure enough no voltage so I ran a hot wire to the pump and it starts running then. Disconnect the wire and it stops again. The only way I had to check the power to the plugs was to pull a plug wire and check it there. Basically meter for voltage. The mechanic i took it to, found the same things I had found. No power to fuel pump or to spark plugs. Please help. Thanks.

 

The fuel pump will not necessarily run with the key in run position. May get 2 second run time at crank but after that i think pcm needs to see a rpm signal in order to run the fuel pump. If the timing belt is broken then you should be able to check very easily by removing the distributor cap and seeing if the rotor turns while cranking the engine. Left bank camshaft turns the distriubutor and if belt is broken the cam and the distributor will not be turning at crank. For spark check am assuming you pulled plug wire and held close to engine ground to look for spark? Try also checking at the wire from the coil to see if spark is getting to the distributor. If no spark and no fuel still then would still be looking at that main relay. A broken timing belt will not shut off the fuel pump. Post will all info you have. Maybe we can figure this out yet.

 

You sure know a lot about Mazda's. How do you know so much? I finally got my car back from the shop. The rotor is not turning so I do have a broken timing belt. I can not find any up to date repair manuals that show the process for changing the belt. Do you have anything? Thanks for your help. Does Mazda make a non clearance engine. You previouly told me the 93 929 does not have one but I also have a 96 millenia. Does it have one? It has the small v6.