1999 Dodge Van relays clicking

Something has to be wrong with that connection if there is 3.5 volts dropped across it during cranking. 0.2 volts is the highest allowable voltage drop for any single mechanical connection in the high current circuit to the starter in either the positive or negative cable.

Caradiodoc

Other folks should be following this thread too so they will jump in.

Nothing will make sense or be relevent when a battery cable is disconnected. You didn't tell me which cable you measured the 3.5 volts on. If you put one voltmeter probe on the negative battery post, and the other probe on the engine block when a helper tries to crank the engine, you absolutely must not read more than 0.4 volts. If thats the circuit where you had 3.5 volts, there is a loose, dirty, or corroded connection someplace. Moving the probes toward each other one mechanical connection at a time will identify the bad connection.

If I'm misunderstanding where you're finding that 3.5 volts, and you actually have less than 0.4 volts drop on the negative side, do the same thing on the positive side. Put one probe on the positive battery post and the other one on the large stud on the starter, not the nut or cable terminal. You might need a second person or a clip lead unless your arms are real long.

Just to verify, the starter relay is still rapidly clicking, and battery voltage during cranking is still over 10.0 volts. If this is wrong, tell me what's happening.

One thing that might be having an affect on finding this problem is taking voltage drop measurements when the starter relay is chattering. The high current to the starter is turning on and off so the voltage drop will be too. That can make the voltage reading bounce all over and be confusing. To avoid this, you can pop the starter relay's cover off, then squeeze the contact with your finger. That will keep the starter engaged so your voltmeter readings will be accurate.

Also double-check what happens to the headlights. They will flicker but should stay fairly bright. If you find they go out or very dim, that suggests the starter is shorted and drawing unusually heavy current. That will cause the starter relay to chatter due to the battery voltage being drawn down, but that would contradict the 10.4 volts you found earlier.

Caradiodoc

WHAT! Do you mean to tell me the engine is cranking just fine but won't run? I thought we were diagnosing a failure to crank with a chattering starter relay. That is a real common problem caused by a weak battery, dirty cables, or a defective starter. If you tell me it's not the starter relay that is chattering, I'm going to feel foolish for not double-checking.

Let's start over with a new approach. Remove the ASD and fuel pump relays, then crank the engine and see what you have for symptoms. If the engine spins normally, the battery and cables are not the problem and I apologize for wasting your time in that circuit. If the engine does not crank normally, remove the cover from the starter relay, reinstall the relay, then squeeze the contact. You can leave the ignition switch off. Now see how the starter acts. If it cranks real slow, finish up looking for the voltage drops in the positive battery cable the way you did in the negative circuit.

Once you have verified the starter is working normally, reinstall the ASD and fuel pump relays, then crank the engine again. If those relays are chattering, disconnect the crankshaft position sensor and the camshaft position sensor. Crank the engine again. If the relays stop chattering, suspect a problem with one of those sensors. If you remove the crankshaft position sensor, be aware a paper spacer must be installed on the end of it to set the air gap. It could break if that spacer isn't used.

Caradiodoc

There can also be a small plastic rib on the end to set the air gap. That rib will partially wear away when the engine is started. If that style is removed and reinstalled, the remaining part of the rib must be cut off and the paper spacer stuck to the end. The Dodge dealer's parts department has them. Some new sensors come with the paper spacer already stuck on. It slides off as soon as the engine is cranked, but its job is done by that time.

My reason for mentioning that is someone had two new sensors crack in half before he asked for help. They were both used sensors he was using and didn't have any type of spacer so the sensor hit the flexplate.

Caradiodoc