1yr ago, tried to start the Caravan that had sat for a couple of years without being started. For diagnostic reasons that I can't remember now, but which I'm pretty sure involved introducing gas directly into fuel rail (using an OTC air pressured canister) and getting van to start, I replaced the fuel pump. Van then started a couple of times over a few days and then wld not start again. Now, a year later and after more diagnostics done, have determined that a.) No power is getting to fuel pump when relays are plugged in (except for quick 12 burst); b.) Replacement pump does not respond when relays are by-passed and power is present at the connector near the pump, so possibly whatever caused the first pump to fail also fried the replacement one; c.) Confirmed that fuel pump and ASD relays are working to the extent that the electromagnets inside do switch over the load side of the relay when there is at least 9v present, but not when it drops below that level; d.) When cranking, the engine voltage drops to below 9 volts after a quick 12v spike, the latter which I now understand (from reading caradiodoc's other posts) is normal until the engine starts running. However, what I don't know is if the voltage is supposed to return to close to the 12 volts after the engine starts. I presume that it cannot be normal to drop as much as it does for me. So it seems that the reason for the lack of power to the pump is that the relays are not switching on the load side because they are getting voltage at the Power Distribution Center that is less than the 9v+ required to energize the electromagnet inside.
Additionally, now the van will not go into reverse. Nothing happens (no jerks, no noises) when in reverse other than the back-up lights come on. Forward drive may be slow in reacting as well, but it does kick in. This new problem occurred on a very cold day after a prolong cold spell of single digits temperatures. Could temperature have been a factor?
Finally, the van has a new coil, new plugs, new plug wires, and a fairly new, but possibly dying battery (not sure if it is holding a charge as well as it should). As I said, the van starts if I by-pass the fuel pump and run it off gas being fed directly into the fuel rail. And speaking of being able to start it, what I have not tested (bc it just occurred to me!) Is to see what the voltage at the PDC is on the electromagnet side of the relays once the engine is actually running - that is, is it between the 9v and 12v needed to energize the relay or below that threshold.
So, what could be causing the voltage drain at the PDC that is failing to activate the relays? A sensor failure elsewhere, the computer, a short somewhere? I have a new Bosch fuel pump waiting in the wings to replace the apparent faulty one, but I do not want to do so until I can ensure there are no shorts or some other fault that may have fried the first two. Any help in troubleshooting this further would be greatly appreciated.
have the same problem?
Sunday, January 12th, 2014 AT 11:11 PM