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Car Forum / Chrysler Cars / December 200494 Caravan - fuel pump won't run
The van has been sitting for a while, but started fine 2 weeks ago. A few days ago it cranked fine, but the fuel pump didn't do the normal 2-second pressure up when the key was first turned on. I can get the fuel pump to run if I jumper the fuel pump relay, so the wiring to the pump and the pump itself seem to be OK. I tried swapping the ASD relay with others (they all have the same PN, and all show the same resistance between the coil terminals), but nothing. I tried jumpering from B+ to the coil +, still nothing. What else can I try? Is there a fuel pressure sensor that thinks the pressure is up, so doesn't tell the pump to run? I don't think it's the Hall effect, since it doesn't come into play until it starts cranking. Thanks KC I forgot to specify engine - it's the 3.0 V6. KC > I can get the fuel pump to run if I jumper the fuel pump relay, so the > wiring to the pump and the pump itself seem to be OK. I tried swapping > the ASD relay with others (they all have the same PN, and all show the > same resistance between the coil terminals), but nothing. I tried > jumpering from B+ to the coil +, still nothing. What else can I try? Remove the 60-pin connector from the SBEC and inspect the pins and sockets for corrosion; clean the pins by pushing a pencil eraser straight down onto each pin, and packing the sockets full of Ox-Gard or Noalox. Check all of the fusible links carefully; it sounds like one or more of them may have popped. Of course if this is the case you'll have to find the cause or the new link will pop, too. > Is there a fuel pressure sensor No. > I don't think it's the Hall effect, since it doesn't come into play > until it starts cranking. I don't think it's the Hall Effect Pickup, since the 3.0 doesn't use one. The 3.0 does tend to develop problems with the *optical* pickup in the distributor, and with the wiring between the distributor and the SBEC, so you can check for that by disconnecting the battery negative cable for a few minutes, reconnecting it, cranking the engine and then checking the flash codes. However, that probably isn't the problem since you say the fuel pump isn't energized with initial key-on. To check the computer codes: With the engine off, switch the ignition key on-off-on-off-on, leaving it "ON". Do not go to "start", just "on" during this procedure. Watch the "Check Engine" or "Power Loss" light. It will turn on, then go off, then will begin to flash-out any trouble codes that have been stored. For instance, if it flashes: flash <pause> flash flash <long pause> flash flash flash <pause> flash flash flash flash flash <long pause> flash flash flash flash flash <pause> flash flash flash flash flash Then you have a 12 (one flash followed by two) a 35 (three and five) and a 55 (five and five). 55 means "end of codes" or, if by itself, "No codes stored. Check the codes and report what you find. > Remove the 60-pin connector from the SBEC and inspect the pins and sockets > for corrosion; clean the pins by pushing a pencil eraser straight down [quoted text clipped - 5 lines] > > Check the codes and report what you find. Thanks for the tips, Daniel. I'll try these tonight and hopefully get it going. I wanted to donate it to my church (they in turn donate it to those who need cars but can't afford them), but they won't take it if it isn't running. And since I can't sell it (tried twice, can't even get an offer at $800, and it's in pretty good shape), and it's not doing me any good sitting in my driveway, this seemed like a good option. Just curious - what is it that tells the fuel pump to quit pumping before the engine starts? The pressure regulator only holds the pressure at a certain level and returns the excess back to the tank, right? But that's with the pump running continuously. Something tells it to stop when the key is on but the engine's not running. KC > Just curious - what is it that tells the fuel pump to quit pumping > before the engine starts? The pressure regulator only holds the > pressure at a certain level and returns the excess back to the tank, > right? But that's with the pump running continuously. Something tells > it to stop when the key is on but the engine's not running. The initial "Bzhhhhht!" that you get from the pump when you turn on the key is just a timed pump pulse of (nominally) 1 second. The purpose is to pressurize the system for engine startup. It's not necessary to monitor the pressure, because as you know, the pressure regulator makes sure there's no overpressure. DS (((Just curious - what is it that tells the fuel pump to quit pumping before the engine starts?))) If the PCM doesnt see that the engine is running after 3 seconds, it shuts down fuel and spark thru the ASD relay, You know that you are getting fuel but possibly loosin spark, go to the windshiled wiper resorvoir and under neath it is where you will locate the fusible links, look at them and gently pull on each one to see if any are broken/burnt.If all ok Check b+ to PCM with a test light for voltage.If ok Check the 5 volt power supply to the sensors for a short to ground. A short to ground on the 5 volt power supply to sensors such as: MAP, TPS, A/C PRESSURE TRANSDUCER, EGR POSITION, etc. will cause the vehicle to die out and may cause the PCM to be a no response. All this of course would be easier using a scan tool to see acuall values and be able to acuate spark and fuel systems, so taking it to a repair facility may be the next option. Good Luck Glenn Beasley Chrysler Tech > > Remove the 60-pin connector from the SBEC and inspect the pins and > sockets [quoted text clipped - 25 lines] > > KC > Remove the 60-pin connector from the SBEC and inspect the pins and sockets > for corrosion; clean the pins by pushing a pencil eraser straight down [quoted text clipped - 12 lines] > Watch the "Check Engine" or "Power Loss" light. It will turn on, then go > off, then will begin to flash-out any trouble codes that have been stored. Update: removed the SBEC connector and cleaned it, didn't see any signs of corrosion. While I had access, I unplugged and replugged all the electrical connectors under the battery. Then put everything back together. Still no fuel pump. Tried to get the codes to flash. Several times. Nothing. Jumpered the fuel pump relay so the pump runs whenever the key is on. Won't start. That indicates to me that there's no spark. Verified that with a timing light. So am I down to fusible links? The only one I saw was one to the alternator, so I must not know where to look. Seems strange that the computer won't blink, though - it should at least give the 55=end of codes, right? I'll go back at it tomorrow, check any fusible links and the wiring to the distributor. KC > Update: removed the SBEC connector and cleaned it, didn't see any > signs of corrosion. While I had access, I unplugged and replugged all > the electrical connectors under the battery. Then put everything back > together. Still no fuel pump. Tried to get the codes to flash. > Several times. Nothing. Excellent indication that you've got a blown fusible link upstream of the SBEC. Common causes of this include (but are not limited to): -Oxygen sensor wires shorts to one another or to ground (can happen if they fall on the hot exhaust manifold) -Radiator or condenser fan motor seizes > Seems strange that the computer won't blink, > though - it should at least give the 55=end of codes, right? Not if it's not getting power, which it evidently is not! Let's make sure we're not jumping the gun, though -- check the pull-apart main disconnect in the positive battery cable about 5 inches down from the battery terminal. It feeds everything *except* the starter. Lift its locking tab and pull it apart. If it is internally broken and/or corroded, clean it up or replace the battery cable assembly. DS > Excellent indication that you've got a blown fusible link upstream of the > SBEC. Common causes of this include (but are not limited to): > Let's make sure we're not jumping the gun, though -- check the pull-apart > main disconnect in the positive battery cable about 5 inches down from the [quoted text clipped - 3 lines] > > DS I don't find that on mine. The clamp has 2 cables - one goes to the starter, the other to the fuse block, with a junction there to another large wire that goes to the alternator. So everything but the starter must be fed from the fuse block. Sounds like I should look between the fuse block and the SBEC for a fusible link, somewhere inside that wire bundle. Or does it run to the fuse block under the dash before it comes back to the SBEC? Seems like a bit of a mess until I look under the dash of my 95 Isuzu Trooper, then it seems like a model of simplicity by comparison! KC > > Let's make sure we're not jumping the gun, though -- check the > > pull-apart > > main disconnect in the positive battery cable about 5 inches down > > from the > > battery terminal. > I don't find that on mine. It's possible someone replaced the cable in the past with a non-factory item. The factory cable assembly has the plastic pull-apart disconnect. > starter, the other to the fuse block, with a junction there to another > large wire that goes to the alternator. So everything but the starter > must be fed from the fuse block. Check for power at the fuse block! > Sounds like I should look between the > fuse block and the SBEC for a fusible link, somewhere inside that wire > bundle. Yep. Probably orange or white. DS >>Excellent indication that you've got a blown fusible link upstream of > [quoted text clipped - 30 lines] > > KC Might be faster to first use a multimeter to check for voltage on the supply pin to the computer. That is faster than tearing into a bundle of wires. Matt > Might be faster to first use a multimeter to check for voltage on the > supply pin to the computer. That is faster than tearing into a bundle > of wires. > > Matt Good idea, Matt. There's power to the fuse block, all the lights and gauges and everything else works fine. With the key on, there's power to 4 pins of the SBEC connector - 3 on the left side bottom row, 1 just above them on the middle row. So there's power to the SBEC, but it won't flash codes and won't turn on the fuel pump or spark. Sounds to me like it's time for a different SBEC. Opinions? KC >>Might be faster to first use a multimeter to check for voltage on the > [quoted text clipped - 14 lines] > > KC First you need to check the schematic in the FSM to ensure that the 4 pins that have power are the only ones that should have power. If the SBEC needs power at 5 pins, then it may not be the SBEC. Matt > There's power to the fuse block, all the lights and gauges and > everything else works fine. With the key on, there's power to 4 pins of > the SBEC connector - 3 on the left side bottom row, 1 just above them on > the middle row. So there's power to the SBEC, but it won't flash codes > and won't turn on the fuel pump or spark. Sounds to me like it's time > for a different SBEC. Opinions? Looking at the 60-socket connector with the wires facing away from you, the cavities are numbered thus: Top row (all the way across, disregarding the central bolt post): 1 (left) through 20 (right) Middle row (all the way across): 21 through 40 Bottom row (all the way across: 41 through 60 Cavity 3 (top row, 3rd from left): Direct battery voltage Cavity 11 (top row, immediately to right of central bolt post) AND Cavity 12 (immediately to right of cavity 11) are the grounds. Check for continuity between them and battery negative. DS Grounds are good, but no power on pin 3 with key on. Also, found a little corrsion on 2 pins at the firewall connector, and more when I pulled the boot back. Cleaned them up, but made no difference. Where does the red and white wire for pin 3 go? I expected to see it coming through the firewall connector, but didn't. Is it time to rip the bundle apart? Are there fusible links in there? KC In article <1103400424.314569.253020@c13g2000cwb.googlegroups.com>, > Grounds are good, but no power on pin 3 with key on. Also, found a > little corrsion on 2 pins at the firewall connector, and more when I > pulled the boot back. Cleaned them up, but made no difference. Where > does the red and white wire for pin 3 go? The "engine" fuse IIRC. > I expected to see it coming > through the firewall connector, but didn't. Is it time to rip the > bundle apart? Are there fusible links in there? A 94 Caravan has but one fuse link; the one between the alternator output stud and the battery. Everything that -was- protected by fuse links the year before is protected by fuses in 94. You -did- check all the fuses didn't you? > > Grounds are good, but no power on pin 3 with key on. Also, found a > > little corrsion on 2 pins at the firewall connector, and more when I [quoted text clipped - 10 lines] > output stud and the battery. Everything that -was- protected by fuse > links the year before is protected by fuses in 94. That explains why I am talking about fuselinks, my newest minivan electrical repair was to a '92. Thanks for clearing that up. DS > You -did- check all the fuses didn't you? Yep, checked em. I expected the SBEC to be powered by the "ignition" fuse under the dash, but that one has power and a good fuse. But pin 3 isn't connected to any of the pins in the firewall connector, that's why I'm confused. There aren't any matching red with white stripe wires in that connector, so if it's supposed to be connected, it isn't. I guess I can pull apart the wire bundle and track it down. KC > > You -did- check all the fuses didn't you? > Yep, checked em. I expected the SBEC to be powered by the "ignition" [quoted text clipped - 3 lines] > wires in that connector, so if it's supposed to be connected, it isn't. > I guess I can pull apart the wire bundle and track it down. You may want to jump battery + to pin 3 and see if the SBEC will power up. In article <1103419468.743793.245210@f14g2000cwb.googlegroups.com>, > > You -did- check all the fuses didn't you? > Yep, checked em. I expected the SBEC to be powered by the "ignition" [quoted text clipped - 5 lines] > > KC It may have been mentioned already, but I can't find it in the old posts. Which engine is in this thing? I'll print the wiring diagram and post which pins have battery voltage and which pins are powered by the ignition switch. But I need to know which engine for your benefit so you don't go on a wild goose chase. > It may have been mentioned already, but I can't find it in the > old posts. Which engine is in this thing? He's got the Mitsu 3.0 > I'll print the wiring diagram and post which pins have battery > voltage and which pins are powered by the ignition switch. > > But I need to know which engine for your benefit so you don't go > on a wild goose chase. It's the 3.0 V6, 2WD. Thanks for the help. KC In article <1103477694.011922.8210@c13g2000cwb.googlegroups.com>, > > I'll print the wiring diagram and post which pins have battery > > voltage and which pins are powered by the ignition switch. [quoted text clipped - 6 lines] > > KC Okay, a 3.0 it is... Pin 3 gets 12 volt battery feed via the 15 amp 'engine' fuse in the underhood power distribution center. This should be 12 volts all the time. Pin 9 is 12 volts ignition feed (ignition switched) via the 10 amp #16 fuse in the instrument panel fuse block. This should be 12 volts with the ignition in the start or run position. Pins 11 and 12 are power grounds. > Okay, a 3.0 it is... > Pin 3 gets 12 volt battery feed via the 15 amp 'engine' fuse in [quoted text clipped - 7 lines] > > Pins 11 and 12 are power grounds. It's supposed to be above 5 degrees this evening, so I'll try to get back to it. I seem to remember at least 2 other pins being switched 12V, though - maybe like 31-32, or 32-33? It sounds like pin 3 is the problem child, though. KC In article <1103552000.184139.276580@f14g2000cwb.googlegroups.com>, > It's supposed to be above 5 degrees this evening, so I'll try to get > back to it. I seem to remember at least 2 other pins being switched > 12V, though - maybe like 31-32, or 32-33? It sounds like pin 3 is the > problem child, though. Pin 31 is 'Low speed fan relay'. Pin 32 is empty. Pin 33 is for 'cruise control'. If pin 3 is dead, and the engine fuse in the PDC has no voltage on either side, I'd be checking inside the PDC for a broken buss. Check the ignition switch, check the bulk head connector, for 12 volts on both inside and outside of it, > In article > <1103552000.184139.276580@f14g2000cwb.googlegroups.com>, [quoted text clipped - 10 lines] > If pin 3 is dead, and the engine fuse in the PDC has no voltage > on either side, I'd be checking inside the PDC for a broken buss. > Check the ignition switch, check the bulk head connector, for 12 volts on > both inside and outside of it, The ignition switch has nothing to do with B+ voltage on pin 3 of the PCM. Found it. The red/white wire feeding B+ to pin 3 of the SBEC was corroded badly about 5 inches from the SBEC. I was pulling on it to get a little slack to jumper it, and it broke. Green copper doesn't conduct well, apparently. Strange place to corrode, but there it was. I jumpered it to the correct fuse in the box (soldered, heatshrinked, and taped), and it started right up. Thanks to all you guys for the help, especially Daniel Stern and aarcuda. Trying to fix electrical problems is next to impossible without the factory wiring diagrams. Plus, a logical approach to troubleshooting really helps. Signing off for now KC In article <1103647425.625054.211130@c13g2000cwb.googlegroups.com>, > Found it. The red/white wire feeding B+ to pin 3 of the SBEC was > corroded badly about 5 inches from the SBEC. I was pulling on it to [quoted text clipped - 10 lines] > Signing off for now > KC Excellent! > Grounds are good, but no power on pin 3 with key on. Bingo. No power to the SBEC. (Did you check your O2 sensor wires for shorting?) > Also, found a little corrsion on 2 pins at the firewall connector, and > more when I pulled the boot back. Cleaned them up, but made no > difference. Where does the red and white wire for pin 3 go? Oof. I don't have '94 minivan wiring diagrams. Start a-followin' it back until you come to the problem (probably a burnt fuselink) Unfortunately, the fuselinks are within the bundle. > Grounds are good, but no power on pin 3 with key on. > [quoted text clipped - 9 lines] > > Unfortunately, the fuselinks are within the bundle. I agree with D.S., trace the Red/White wire back to the battery. Looking at the 1991 wiring diagram, I'll bet it's very similar with the possible exception of a fuse instead of a fusible link. It should be powered at all times, not just when the ignition is on. The diagram shows that pin #3 has a red/white wire that goes back to a 22 gauge white fusible link, then changes to a 10 gauge red, then to a junction at a 6 gauge black (battery feed). Trace it back and find where you're loosing continuity. Run the hot lead from the pump to the + coil terminal. The pump should run whenever the engine does. A more elegant solution is to wire in a Bosch lighting relay. Wire the relay coil to ground and coil +. Wire the contacts from Batt to pump hot wire. Whenever the ignition runs, the pump runs. Good enough for a free car. Paste a label on the dash "Run this car at own risk" so you're off the hook. |
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