Chrysler Repair/'93 2.5L 4 cyl: no start
QUESTION: 1993 dodge shadow 2.5 automatic. Was running when parked but didn't restart. Have spark and starts when gas is poured in throttle body, fuel pump relay clicks only in start position, voltage at fuel tank shows only when cranking. Relay has been interchanged with one from another dodge that starts and runs.
ANSWER: Hi Mike,
The voltage to the fuel pump will only occur as follows:
for about 2 seconds when you turn the key to run you will hear it hum,
when you try the starter it will be powered as long as the starter is turning and you have a good signal from the distributor rotational sensor,
when the engine starts and runs on its own power.
It may well be that the hall effect sensor in the distributor is flakey and although producing spark it is not 'solid' enough to keep the Autoshutdown relay activated. That ASD relay is a fire safety device that disable the fuel pump and the spark coil voltage supply when the engine is not rotating (and of course the rotational sensor has to be putting out a good signal too).
I would try for a fault code readout using the ignition switch:"on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the check engine light, which remains 'on', to see it begin to flash, pause, flash, etc. Count the number of flashes before each pause, then repeat the process to be sure you have an accurate set of flash counts. Tell those counts and we'll go from there.
Another possibility is that your 'mixture' is too lean because the exhaust gas recirculation valve is stuck slightly ajay. From the front side of the engine go around to the firewall side where you will see that valve mounted vertically. Notice that there is metal rod hidden behind a flange that separates the round top with the vacuum hose attached to it from the valve's body proper. That rod is the valve stem and it has a circumferential slot in it. Put the tip of a screwdriver in the slot and move the rod up and down to free up its 'action'. Spray some WD-40 on the rod where it enters the valve body and move the rod some more to be sure that the internal spring-action moves it firmly to the closed position. Then see if the engine will start.
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QUESTION: Hi Roland, thanks for the help, I appreciate it greatly !!
I checked the codes when the car first did not restart and I checked them again as you requested and got a 55 end process code both times and a 12 code the second time because I had disconnected the battery, cleaned the terminals and recharged it. I exchanged the hall effect module with one known to be working from a friends Dodge Shadow and still had the same results. I cleaned all terminals on ASD and fuel pump relays, I checked the voltage again at the tank terminals with both analog and digital meters and got .1 volts (point one) for a short duration with the key in run position and 12 volts in start position. The EGR valve was moving freely.
Thanks again for any advice.
ANSWER: Hi Mike,
Since you have spark and fuel pump action, the only other possibilities are the fuel injector in the throttle body. If you remove the air filter housing you can observe its function. While you are cranking it over you should see a very fine symmetrical spray falling on the surface of the throttle plate. If not, or if it is dripping down after you stop cranking, then you have a defective injector. I've had that happen on my '89. Also if that doesn't reveal a problem you might have a MAP sensor which is inaccurate but not so badly as to set a fault code. I've had that too, and you would need to check the MAP signal to see if it is showing about 4.7V (but could be a bit lower if you are at high altitude). You also could check the fuel pump pressure which should be around 39 psi.
Please "rate" my answer (see the PS below). I would very much appreciate a 'nomination' for 'volunteer of the month'.
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QUESTION: Hi Roland,
Thanks again for the help. The MAP is showing 4.99 volts. (I'm at sea level) My focus now is the fuel pump, there is no way .1 volts (one tenth volt) , which is the voltage at the pump when the key is first turned "on" ) is going to energize the fuel pump for me to listen to hear it whirl.I did place a hose in the tank an had someone crank the engine while I listened but heard at lot of wind and starter noise which made it difficult to determine if the pump was working. My question is: if I place an ammeter in the pump circuit (which is showing 12v cranking voltage) and get no current measurement, should I assume the pump is defective ?
p.s. I did vote for you and rated you 10 because you're the man !!!
That initial voltage to the fuel pump (and the spark coil, etc.) only lasts for a second so if you are measuring for it at the moment you turn the key to run and you don't see it then that could be an issue with the pcm but the fact that it does show 12v when cranking suggests that nonetheless it will produce pressure needed to produce output at the injector (if the pump indeed runs). Why don't you remove the fuel pump relay and jump a wire across from the rear pin socket to the front pin socket (red/white to dark green/white wires viewed from underneath the socket) and listen for the hum of the pump without the background noise from the cranking over. That would be easier than measuring current and you might exceed the range of your ammeter and damage it. Be careful not to short that rear red/white wire to ground when doing that because you will blow a fusible link if you do.
Again, have you observed the spary I described inside the throttle body? That is the bottom line you are looking for as to whether you have fuel injection.
The MAP 4.99 would be of concern but I didn't tell you where to measeure that so you may have measured the sensor's operating voltage (5v) rather than the signal voltage. The MAP signal is measured between the two outside pins at the sensor plug, or between pins 1 and 4 at the pcm plug. Use a couple of fine pins to pierce through the insulation to read the signal with the key in the run position. The wire colors are violet/white and black/light blue. If it really is 4.99 then the MAP signal is clearly improper at sea level because mine reads 4.67 at sea level, or possibly the 5v wire is shorted to the signal wire somewhere in the harness.
Thanks so much for the kind opinion of me. You can even do it again for this answer!