1996 Dodge Dakota Fuel Pump Power Issue

relay guide wiring diagram

Sorry for the delay issakar. First I had trouble saving the pics because they are PNG which only show on screen, not when viewed from the saved file. (Or is that just me; I've forgotten "copy-protection" stuff - but not print-screen as bitmaps and good old MS Draw.) Then those rotten IEC contact symbols. But the "capacitor" and "variable capacitor" symbols on the FUEL PUMP RELAY merely mean a normal SPST contact/switch. Conclusion(s): You can use an SPST relay but it should have a Protection Diode. SPST relays with protection diodes are common. Else you could buy your own (eg) 1N4004 or 1N4007 diode (~20c each - I suggest a few spare; & they can be useful for other things...) and wire the diode into the base. There are no resistors etc. Wiring confirmation (for Bosch type relays; see diagram)... 5A to #86 5C to #85 5B to #30 5D to #87 No indication of current rating and 15A should suffice, but I suggest the (more?) common 30A type - ie a 12V/30A SPST relay. [ POST EDIT - I have updated with the above diagram. I hope it makes sense, and isn't wrong! ] The rest hereunder is trivial... "AUTOMATIC SHUT DOWN RELAY OUTPUT" (FUEL TANK MODULE C327) is a crappy name for "the Fuel Pump". And "FUEL TANK MODULE"' is a crappy name for a "Fuel Tank". The former is NOT an output and the latter is NOT a module (IMHO). "From (or To) AUTOMATIC SHUT DOWN RELAY OUTPUT" and "FUEL TANK Assembly" may be acceptable. But I'd prefer "From FUEL PUMP RELAY" or better still, simply "Fuel Pump" and "Fuel Tank". It's a simple wiring diagram!    (Per chance, did Microsoft write their documentation?) Personal Conclusion - I should just analyze on screen instead of thinking I always need to print diagrams and legends. Only one "block" in the relay guide was relevant (d'oh!) and the wiring diagram was easy (d'oh #2!) FYI - the circuit is "typical". The fuel pump is powered from the (fused) battery (#30, 5B) thru the relay (#87, 5D). It's a "hot" coil - ie, Ignition +12V to #86/5A - which is grounded (#85/5C) by the C19 FUEL PUMP RELAY CONTROL (POWERTRAIN CONTROL MODULE; C175) to turn the pump on. (Probably an "Open Collector" transistor; it "floats" when off and shorts (connects) to GND when on. That is typical for digital EMS/ECU etc outputs.)

Oldspark, Thanks again for your continued support in resolving my issue. I really appreciate it and I am learning a lot! To think just a few weeks ago I couldn't even begin reading a wiring diagram, lol. Do you think it is possible that all my issues could be related to a poor ground? I feel like yo may have mentioned this as a possibility previously but I don't recall right this second if that is so. I havn't tried my direct wire test yet due to a busy schedule and poor weather. I should have time this week, wednesday by the latest to really give it a shot and see what happens. thanks again, I really appreciate you sticking with me through this!

issakar wrote: To think just a few weeks ago I couldn't even begin reading a wiring diagram...

THAT is what makes it so worthwhile and rewarding! That is what the12volt strives to do. Solving the problem is one thing, but to make people realise what they are capable of... (I think that's called edukashun. Or is it self-actualisation & -realisation?) But enough of my young(cough!) innocent (cough cough!) naive idealistic rambling! A bad ground? Oh yes - definitely. The common and evil ground-gremlin is probably the most basic yet confusing, damaging and subversive bug to exist in any electrical system! [ Yes - it's true - Gremlins are really bugs! (Trust me...) ] I did mention it - probably because I was lucky enough to remember the in-obvious obvious potential (pun intended - potential as in voltage).    And I suppose ~36 seconds would be enough for me to look back and check, but who has time for that?! Check the voltages at FUEL TANK MODULE terminals 4 & 6 with POWER DISTRIBUTION CENTRE 5B shorted to 5C. They should near 0V. Perhaps 1V max (assuming the Fuel Pump is drawing its current). BTW - I used the expert-TECH SPEAK you and now I are so familiar with. But let's keep the translation to ourselves!      The rest hereunder is optional reading... A grounding in grounding: Picture a ground as a resistor. It can be perfect - ie, zero resistance; bad can be from a fraction of an Ohm to many Ohms; or open-circuit (ie, infinite resistance/Ohms). If open, the "thing" shouldn't (or won't) work, and all voltages upstream should be "high" and the same. [ Open means zero current means zero voltage drop. Ohms Law: V=IR "The voltage across a device equals its resistance times the current going through it. ] If perfect, we don't care. The "ground" voltage drop will be zero. (V=IR; if I = 10A, then V = 10 x 0 = 0V because "perfect" is zero Ohms/Resistance.) But in practice, everything has resistance, but ground and power resistance should be small enough to minimise the voltage drops (which increase with increasing load/current). Power grounds should me milli-Ohms if that. EG - for 10A & 1mR, V=IR = 10A x 1mR - 10mV = 0.01V (or 10 x 0.001 = 0.01V). NOTE - I am using "R" instead of the Ohm symbol Ω because I couldn't be bothered finding it... I mean, Ω can have problems in different fonts or applications, and since we don't understand foreign languages and R is on our keyboards anyway.... Where was I....? Oh yeah, a 0.01V drop in a 12V system - bah! nothing, negligible! But if the GND is 1/10th of an Ohm: V = 10 x .1 = 1V. Hey - that's 1V in 12V - we are getting concerned. Fit a 100A load or amp(lifier) to that... V = 100A x 0.1R = 10V. Now we do have a problem! (In practice you won't get that current thru the circuit hence not that "ground drop" - the total circuit resistance limits the current. But that's for another time - let's keep it simple (coughs again!). The point is bad grounds result in UNDER-current and voltage - the load probably won't work - ie amplifier, fuel pump etc. [ In some situations, bad grounds can be damaging. Alternators can overcharge and cook batteries; electronics can fry due to inter-ground currents (across ground voltage drops) etc. ] Hence the "Big 3" etc etc. Trust me, I've tried to get rid of GNDs and electricity return paths but the things just refuse to work! Selfish $#$@s!! - one "feed" isn't enough - they want TWO! Both the "feed" and the "return". They must be of that Greenie recycler clan! (Good!!) (The above was attempted humour.) Rats!   I've already explained the effect of a bad ground in the above example. Never a perfect ground eh? But good enough depends on the circuit.... Oh well, that gives me time & space to say that IMO, get a few "basics" and abilities simply accumulate... The main basics include being able to understand wiring diagrams - including crappy ones! [Break them down; isolate or do one section or circuit or wire at a time. A pencil or colored marker(s) can be godsends - especially on (multiple!) diagram copies!]     Then there is the basic understanding of electricity (that's where the water analogy is excellent!) and that usually involves an understanding of the simplicity of Ohms Law. (The pressure drop along a pipe is proportional to it's size and the amount of water going through it. IE - as size/diameter decreases its resistance increases, and more flow quantity means higher friction and turbulence - ie, higher resistance.) [Water currents and electrical current - coincidence? I think not! (LOL)] Most people "understand" Ohms Law - they just don't realise it. Mind you, applying to a circuit can be tricky (I still get caught!), but you learn the tricks with experience. (Which in retrospect are so damned obvious, but....!!) It is yet again breaking down in to basics - currents THROUGH a device and its "string" OR the voltage ACROSS various devices or strings (and their resistance) to work out total resistance or current. On part at a time... Alas, ramble.    But I am curious if your last "could it be ground?" was a self realisation, or a subtle re-read (and thus flagged or realised). If the former, I am impressed. Though I'm still impressed with the latter - after all, you prompted me, I didn't remind you. And better still, it wasn't a question AFTER buying a new relay, or pump, or battery, or vehicle! But really, though I suspect it was self realisation, who cares? I think your "... couldn't even begin reading a wiring diagram, lol." (ie, LOL) says it all! Good luck - not that luck seems relevant in your case.

Oldspark! sorry about the delay in response, funny how schedules fill up fast! I have had the chance to do some work today and found some pretty interesting results. I made 2 jumper wires today from a spool of wire I got from a person i work with. I put alligator clips on the wires and hooked one to the fuel pump positive side. I then hooked the second one to the fuel pump ground and the other side of the wire to a section of the frame of the vehicle i had lightly sanded until it was nice and shiny, bare metal. As a precaution, I unplugged the PCM connectors to be sure I didn't fry anything. Once the pump was all hooked up, i attached the "positive" jumper wire to the B+ (12v) battery terminal (positive). As soon as the clip came in contact with the B+ the pump hummed right up! I am really thinking this is a ground issue at this point. btw [quote]But I am curious if your last "could it be ground?" was a self realisation, or a subtle re-read (and thus flagged or realised). If the former, I am impressed. [/quote] in answer to that, it was more of a self realization. I was beginning to suspect a ground issue, but was not 100% sure. I asked that looking for a confirmation of if i was on the right track. I really think I am! What I am going to try next is putting everything back together, and leaving the pump connector off. Then I am going to connect a jumper wire to the feed side (pin 1 on the fuel pump connector C327) and to the pump pin 1. then i will keep the same ground to the frame setup I have right now. I will reassemble the PDC, reconnect the PCM, hook up the battery and crank her over. My hypothesis is that this truck will then start up! I'll keep you informed on what happens as I get a chance to do it. I really appreciate all the advice and info, and always look forward to more! Thanks again Oldspark!

Well Oldspark I got excited too soon. I have figured out that this most likely ISNT a ground issue and here is how. I reconnected the existing wiring and such and ran a jumper from power pin to the pump and left the pump grounded out to the frame. NO PRIME. I checked voltage at that connector grounded to the frame and only 6-7v. So I am losing A LOT of voltage somewhere along the way. very intersting. I am thinking about just running new wiring for the pump. None the less I still want to try and find out whats going on! lol

POST EDIT - I missed your last reply (probably because I was out rewarding the crows mid-reply), but it sounds like you "have it under control" - it's a seek&destroy issue; much as described below... /end POST EDIT

issakar wrote: As soon as the clip came in contact with the B+ the pump hummed right up!

Congratulations! I hereby declare you honorary mechanic! [ A useless & qualified mechanic ~2 years ago claimed "fuel pump problem" on my mate's car despite my protestation, AND check methodology. Anyhow, 2 weeks later, one blown EMS-CPU later, my mate was the one that found the causal battery-fuselink problem. This ignoramus mechanic couldn't even jumper-lead a fuel pump! ] As to "...it was more of a self realization. I was beginning to suspect a ground issue, but was not 100% sure" - good! That suggests "thinking" - a rare commodity these days. With that comes accelerated learning. And sometimes caution is warranted.... "a little but of knowledge..." (can be a dangerous thing). "I am really thinking this is a ground issue at this point" Be careful - it can get confusing. If the pump buzzes fine when jumpering the +12V feed ONLY, the GND is ok (probably). If whatever you jump changes things, then that <whatever> is the problem (in "simple" systems). But there is the possibility that the relay coil has a grounding or power problem. VIZ - poor IGN +12V or poor control GND thru the Powertrain Control Module, hence coil/field not at full strength and the relay contacts are too light or chatter - hence contact failure. But that's why a DMM to measure voltage drops across each section in operation is invaluable. But certainly #4 & #6 at the fuel tank should be GND ie, 0V (or well under 1V? to chassis). And C175 (#C19 Pwrtrn Ctrl Mod) should also be GND when the fuel pump should be on (eg, maybe initial IGN on for a few seconds and then when engine is cranking, and running; but NOT when is stalled). As to delayed schedules - ha! Tues shifted to Fri; tyres yesterday not today (Thurs); funds that had not been transferred as at Tues had in fact been transferred Monday.... That's my snafu week! (But the local crows/ravens cleaned out a dirty roof gutter. Bonus FTW!)

Oldspark, Check this out. So with my new jumper wires i made (handy things they are) i did a bit more testing. Here is what I found. When i disconnect the lower wiring harness for the truck (works the fuel pump and lights and such. the c207 connector on the wiring diagram) and test the truck side of the connector i get 12v. this is good. it rules out interior wiring (behind the firewall), it rules out PDC issues, etc etc. everything on the top end looks good. Now, if i use a jumper wire and send a direct B+ connection down the line, and check at the fuel pump, guess what? thats right, low voltage- 8-9v to be exact. So as another test, I took my jumper wires (these things are great!) and cut a slit on the insulation for the wire directly below the 207 connector. I did this to test of it was a connector issue or otherwise. same result, low voltage. I left this setup intact and instead of hooking to B+, i connected the "positive" jumper wire lead to the pos meter lead. I then turned it over to continuity mode. I didn't get a reading on continuity. I thought that was strange so i switched it over to the ohms mode. The only way I get a reading on the Ohms mode is if i set the meter to 2000k. Not a typo, two zero zero zero kay. lol. When i have it set to this setting, the reading is around 540, 539, etc. I think I know what this means, but........ What does this mean? Thanks!

Er, I'm pre-coffee, and shouldn't be here... Lots of things come to mind, but beware - breaking the ground C207 should "float" all the "other side" up to 12V since there is nothing to pull that down (to GND). BUT that does not mean all is ok - it just means you have a 12V source at voltmeter currents - ie micro-Amps. It will not detect if there is 1, 1k & maybe even 1M Ohm resistances in the line. IE - start putting current thru that path, and the voltage may drop (burnt relay contacts; bad connections, etc). The 7V readings... I did say I was pre-coffee eh? Oh - I shouldn't be here - I'm off wood collecting.... (Never been so happy for physical work in my life!) Later..... (..." coming dear....") PS - not using Resistance scale on a powered circuit? (That's a no - no.)

Have a good time, I'm off to make dinner and such myself, lol. Different time zones are great, arent they? BTW, no, I did not use the meter on a powered circuit ;) I R Learningz! lol. thanks again!