No power to injectors in throttle body

Tiny
P.MORRIS
  • MEMBER
  • 1991 DODGE RAM
  • 5.9L
  • V8
  • 2WD
  • AUTOMATIC
  • 250,000 MILES
Replaced fuel lines from tank to throttle body. Used high pressure lines for pressure regular line for return. Refueled will not crank. Not getting power to injectors in throttle body. Will crank pouring gas in body, but will not run. Changed relay, new cam sensor in distributor, wires, plugs. Rotor, cap. Took computer out put in another same model truck cranked right up. Cannot find a crankshaft position sensor or any wires going to the areas they should be. Help!
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Wednesday, January 11th, 2017 AT 3:40 PM

30 Replies

Tiny
CARADIODOC
  • EXPERT
You said it does not crank, but it does when you pour gas in? Are we working on a starter problem or a running problem? If the engine is cranking fast enough to start, the starter is working. Have you checked the diagnostic fault codes? Have you checked for spark? Under what conditions are you expecting to find twelve volts at the injectors? What led up to this? Did the problem start after you replaced the fuel lines, or did you replace the lines in an attempt to solve a problem?
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Wednesday, January 11th, 2017 AT 3:54 PM
Tiny
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Will not crank unless pour gas in throttle body but will not catch and run. Had leaking fuel line then rubber lines on ends where fuel filter and at throttle body dry rotted and were leaking ran new fuel injector high pressure line to engine compartment mounted fuel filter there then on to throttle body ran regular gas line back to tank for return. This was the gas leak that I had and fixed it have gas to throttle body. Have fire to plugs, have twelve volts at relay. Have no volts at the two injectors in throttle body. Was told being 1991 cannot hook up a tester 1996 on is all they had. Have changed sensor in distributor, took out computer took to truck same model plugged in cranked fine. Had been running with a mis and lots of raw unburned gas, stomp it black cloud. Changed cap, button, wires, plugs, still ran ragged until I drove it in my shop cut it off dropped gas tank ran new lines put tank back up filled with gas then DUD.I have pulled tank back down re plugged looked for problems none. Took computer out cleaned all pins and other end. Nothing, only guess left is a crankshaft positioning sensor that I cannot find or any wire anywhere around block.
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Wednesday, January 11th, 2017 AT 6:22 PM
Tiny
P.MORRIS
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Had a mechanic come look at it he's also stumped
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Wednesday, January 11th, 2017 AT 6:24 PM
Tiny
CARADIODOC
  • EXPERT
I think you are confusing the issue with your terminology. "Crank" means the starter spins the engine. If the engine runs when you pour gas into it, that means it runs. The next concern is you said you have spark. If that is correct, we are way past looking at the crankshaft position sensor and the camshaft position sensor. Those have to work for the Engine Computer to turn on the automatic shutdown, (ASD) relay. That relay sends current to the ignition coil, injectors, alternator field, and fuel pump or pump relay. The fact you have spark proves the ASD relay is turning on, and it proves there should be twelve volts at the injectors. What a lot of people overlook though is the ASD relay only turns on for one second when you turn on the ignition switch. It turns on again during engine rotation, cranking or running, and the computer knows that by the signal pulses it gets from the two sensors. If you are testing for twelve volts at the injectors, it is best to use a test light because digital voltmeters do not respond fast enough to see that initial one-second pulse. After that, you must be cranking the engine when testing for voltage on that circuit.

Your crankshaft position sensor is in the transmission bell housing, right behind the right cylinder head, but as I mentioned, it has to be working if you have spark. The first thing you must be aware of is if the battery is disconnected or run dead, the Engine Computer loses its memory. Same is true when you disconnected the computer. Chrysler Engine Computers have an extremely low failure rate, so that should be the last thing on your list of suspects. Fuel trim data will be rebuilt as soon as you start driving, but you have to perform a procedure to relearn "minimum throttle". Until you do that, you may need to hold the accelerator pedal down 1/4" for the engine to start. You will not get the nice 'idle flare-up" to 1500 rpm at start-up, and it will tend to stall at stop signs. To meet the conditions for the relearn to take place, drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals.

You are also right that the people at auto parts stores that will read fault codes for you can usually only do that on 1996 and newer models with the on-board diagnostics version 2, (OBD2), emissions system. I am surprised your mechanic does not know that Chrysler makes reading fault codes yourself much easier than any other manufacturer. Cycle the ignition switch from "off" to "run" three times within five seconds, without cranking the engine. Leave it in "run", then count the flashes of the Check Engine light. You will get a single flash for the digit "1", a short pause, then two flashes. That is code 12 and just means the power to the Engine Computer was lost recently. That's because it was unplugged. If there are other codes, they will flash the same way after a longer pause. The last code will be "55" which means "end of message".

Any codes that were in the computer were erased when you unplugged it, so that valuable information was lost. Some codes will not set easily just from cranking the engine. If I had to guess, based on your description of the symptoms, I would be looking at a failing MAP sensor or a cracked vacuum hose going to it. That sensor has the biggest say on fuel metering calculations on Chrysler products. Most other manufacturers have not figured out how to do that. They use the mass air flow sensor instead.

Also, be aware the Chrysler dealer's parts department has repair kits for the fuel filter. You get four fittings, two straight and two curved, four fuel injection hose clamps, and two pieces of hose. You use only the two fittings needed on your truck. If I understand that you moved the filter to under the hood, that is likely to make the hose too short to flex properly when the engine rocks. Heat could be an issue too as it can turn hot fuel to a vapor that cannot be pumped. That is not an issue on your truck because the fuel is constantly flowing through the regulator and back to the tank. The bigger concern is the rubber o-rings in those fittings. When they get cold, they do not flex and stretch well to accommodate the flexing. It is real likely you will find fuel leaking from them until they warm up. Throttle body injection systems run at a pretty low pressure, typically around fourteen pounds, but that is more than enough to spray fuel onto hot exhaust parts.

Check if you have fuel pressure. If you hear the hum of the fuel pump for that first one second, but you do not have any fuel pressure, suspect the two hoses are switched at the tank. I had so many miles on my 1988 Grand Caravan that I had to replace the pick-up screen in the tank twice. Both times I ended up with a crank/no-start because I switched the hoses, and I am supposed to be the expert! If the hoses are switched, you will find fuel spraying from the return hose when you loosen the clamp.
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Wednesday, January 11th, 2017 AT 7:36 PM
Tiny
STEVE W.
  • EXPERT
Okay, crank means the engine turns over when you turn the key. Run means it actually starts and runs. Very confusing when you mix them into the issue.

Unplug the upstream O2 sensor and see if your power returns. The symptoms you had earlier suggest the SBEC couldn't control the fuel. The O2 sensor is on the same feed as is the fuel pump. If it was shorted internally it could cause this issue.

Crank sensor is on the top right side of the bell housing/engine flange area. Simple two wire sensor.
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Wednesday, January 11th, 2017 AT 10:00 PM
Tiny
P.MORRIS
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Engine turns over fine will not run unless pour gas in. Then runs only while that gas is there.
If I loosen hose clamp at throttle body gas will shoot everywhere gas is there under pressure at throttle body. Cannot find crank sensor or two wires going to bell housing area found three sets of wires going to transmission. Looked multiple times unless it is on the very top where there is very little clearance. I am thinking when I had volt ohm meter in injector caps seemed like I was getting like one volt. It would barely move the mechanic had his test light in cap while I turned it over I thought he said it was pulsing? All along I have thought broke wire somewhere, or the hidden crank sensor?
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Thursday, January 12th, 2017 AT 4:28 AM
Tiny
P.MORRIS
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Thanks for the image of crank sensor. I will try again. Thank you so much I have got to get my truck going it is a utility truck with all my tools. If I do not have it it is hard to work.
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Thursday, January 12th, 2017 AT 4:37 AM
Tiny
CARADIODOC
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You are still overlooking the undeniable fact that you have spark. The cam and crank sensors are working, so leave them alone. The only way to have spark is if twelve volts is being fed to the ignition coil. That twelve volts comes from the ASD relay. The Engine Computer turns that relay on when it gets signals from both sensors, and the engine has to be rotating for them to generate their signals.

Which fuel hose are you getting fuel to spray from, the supply or the return hose?
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Thursday, January 12th, 2017 AT 1:56 PM
Tiny
P.MORRIS
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No crank sensor found anywhere. There is not a place where I can find two bolts together that would hold one there is a female plug empty beside distributor with two wires. Mechanic said no pulse on injectors. When I turn switch off an on it blinks slow then fast do I group number of blinks in two's and count until they stop or does it recycle the blinks? It had 123311312323 and I quit counting did not know if recycling or still giving codes.
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Thursday, January 12th, 2017 AT 2:14 PM
Tiny
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Was still blinking.
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Thursday, January 12th, 2017 AT 2:14 PM
Tiny
P.MORRIS
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When take return off no gas. Turn motor over no gas out of return.
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Thursday, January 12th, 2017 AT 2:51 PM
Tiny
CARADIODOC
  • EXPERT
On most models, if you think you miscounted the flashes, you can just turn the ignition switch off, then back on once, and the codes will start over from the beginning. This test mode will continue each time you turn the ignition switch on until the Engine Computer gets a voltage signal from the starter relay circuit. To say that in normal terms, the codes will stop flashing once you crank the engine, even if that is only for a fraction of a second.

Ford's of this era were known to set multiple identical codes one right after the other, but I have never seen that on Chrysler products like you have here with the two "23"s at the end of the sequence. Double-check those codes, but from what I see here, they are:

12 - Memory to controller has been cleared within 50-100 engine starts.
33 - A/C clutch relay circuit, open or short detected.
11 - Camshaft signal or ignition signal, no reference signal during cranking.
31 - Purge solenoid circuit, open or short detected.
23 - Air charge voltage high/low detected.

Code 11 refers to the distributor pick-up assembly. My gut feeling is most of these codes set when something was unplugged for testing while the ignition switch was on. I do not know how you can have spark if the crankshaft position sensor is missing. Ninety five percent of crank/no-starts are caused by a loss of spark and fuel pump/injector pulses, and those sensors are what is in common with both systems. Loss of spark by itself is responsible for about two percent of those no-starts. Loss of only injector pulses is the cause only about three percent of the time. Since you have spark and fuel pressure, watch for a cone-shaped spray of fuel pulsing from each injector while a helper cranks the engine.
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Thursday, January 12th, 2017 AT 3:11 PM
Tiny
CARADIODOC
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You pulled it off from the throttle body? There should be gas pouring from the port on the throttle body during cranking. If there is not, remove the hose leading into the fuel filter. You should see fuel run out of that hose for the one second when the ignition switch is turned on, and again during cranking.
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Thursday, January 12th, 2017 AT 3:16 PM
Tiny
P.MORRIS
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There is fuel at intake under constant pressure, nothing out of return even with hose off throttle body and cranking attempted I will count codes again when I get home till they stop
the cam shaft assembly in distributor I replaced. Was 1 of the only things I could figure that works with injectors. The parts house showed me a pic. Of crankshaft relay and it takes 2 bolts there is nowhere on the bell housing/motor where 2 bolts are together to even mount 1.I have looked closely dozens of times, crawled under, around, thru, I found what I thought was gonna be it with a bolt that goes thru bell housing into block at about 11 o'clock it had a metal brace with a piece of plastic on it that was still attached spent 2 hours until got out and could see it close up looked like a mount holding where a line for the smog pump stuff that I cut loose in 2000. But it was where it should have been but only 1 bolt there. I can feel around the bottom to top along bell housing and block nowhere is there 2 bolts together to mount a relay.I was looking for an internal 1 until the parts place showed me 1 for a different dodge and I realized this is a surface mount that is in a specific place on the outside of bell housing to pick up where it goes by must be magnetic senses thru aluminum bell casing. Thats my quess to understanding that. If the part is on a 1 bolt bracket that is at 11 o'clock that could be it. And right under that vacant female plug behind distributor.I see where 2 bolts would keep it in a specific place. I'm borrowing a truck today to work. I will count flashs this p.M. Again thank you.
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Friday, January 13th, 2017 AT 3:57 AM
Tiny
P.MORRIS
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I just thought and went out while it was dark could see the dash light much better counted till they stopped. 12 33 11 42 55 hope this helps
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Friday, January 13th, 2017 AT 4:08 AM
Tiny
STEVE W.
  • EXPERT
OK, this truck ran fine until you changed the fuel lines correct? After that it wouldn't run correct? What fuel pressure are you getting at the throttle body? It takes a minimum pressure for them to work, as you are getting nothing in the return line I would suspect you are not getting the correct pressure to open the regulator.
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Friday, January 13th, 2017 AT 9:39 AM
Tiny
P.MORRIS
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Finally got to crank but it will only idle for 20 seconds or so then die will not accept gas. I'll play on
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Friday, January 13th, 2017 AT 12:00 PM
Tiny
P.MORRIS
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Now I get 12 33 24 27 then 24 again so i'll get someone with better eyes to count in an hour
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Friday, January 13th, 2017 AT 12:23 PM
Tiny
P.MORRIS
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I'm getting about 10 to 15 lbs fuel pressure just turning over motor turned it 10 seconds and it might have gotten 15 lbs pressure
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Friday, January 13th, 2017 AT 12:49 PM
Tiny
P.MORRIS
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Leaks back to zero immedetely
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Friday, January 13th, 2017 AT 1:04 PM

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