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  #1  
Old July 7th, 2010, 06:48
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kujito kujito is offline
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Unhappy Crank, no start; fuel pump not priming?

'89 4.0/AW4; 200k miles. I'll try to keep it short.

Stalled out while driving. Restarted twice, then no more.
Was thinking CPS/CPK, on the assumption that I had fuel and spark. Verified spark, and had pressure @ schroeder valve on fuel rail. May have been residual pressure though.

This morning she still cranks, but no start. No pressure from schroeder valve and I don't hear the fuel pump trying to prime.

How do I verify whether the pump is bad or not. Specifically, what relays/fuses may be at fault if pump is still good? Is there something that I can short/jump to see if the pump will prime?

Already gonna be late for work; hoping to keep that to a minimum.

EDIT: I get 218 ohms across CPK A & B. Only have DMM (no needle), so checking cranking voltage isn't gonna happen.

Thanks,
Brian

Last edited by kujito; July 7th, 2010 at 06:57.
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  #2  
Old July 7th, 2010, 06:57
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kastein kastein is offline
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Re: Crank, no start; fuel pump not priming?

Hmm... a RENIX.

I hope Joe Peters is on because I am a RENIX idiot, but here goes: find the yellow wire (should be pin 4 of diagnostic connector D2, i.e. the large diagnostic connector) and make sure it has +12V. That's the ignition switched power feed as far as I can tell from the schematic.

If that checks out, find the fuel pump relay and check that you are getting +12V at one side of the coil and ground on the other. If you're not getting a ground on the side going to the ECU (if it's the same as an 88, this wire will be orange with a stripe) then I'm not sure what to do... if you are, check for +12V at the orange-black (or green-something) wire at the fuel pump ballast resistor. If you're getting that I think it's the pump at fault, or a ground or wiring further down the harness toward the pump.
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Old July 7th, 2010, 07:04
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Re: Crank, no start; fuel pump not priming?

Thanks, I'll go poke around for a few.

I plan to go thru the engine bay grounds again (block, firewall, dipstick tube) and clean 'em all up.
Diagnostic connector D2? Location?
Not sure I know which relays are which, and nothing in there is labeled. There are a few identical (looking) relays, so I'll swap 'em around and see if anything changes.
Fuel pump ballast resistor; drivers side fender near air box?
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Old July 7th, 2010, 07:13
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Re: Crank, no start; fuel pump not priming?

The diagnostic connectors are those rectangular nylon connectors under the plastic shield on the passenger side of the vehicle - they should have yellow rubber protective caps over them. You're looking for the larger one, not sure which position pin 4 is but lunghd has this article which may help you: http://www.lunghd.com/Tech_Articles/...iagnostics.htm
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  #5  
Old July 7th, 2010, 07:38
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Re: Crank, no start; fuel pump not priming?

Need to verify that I've got the right relay, but it might be the fuel pump (Thanks FrankZ!). Jumped suspected relay, and no sign of life from the pump.
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  #6  
Old July 7th, 2010, 08:21
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Re: Crank, no start; fuel pump not priming?

Not sure if this applies to renix, but a shorted CPS can short out the ASD relay, which in turn won't let the fuel pump prime. Try disco'ing the CPS and see if the fuel pump will prime when ignition is turned on.
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Old July 7th, 2010, 09:18
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Re: Crank, no start; fuel pump not priming?

no go
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  #8  
Old July 7th, 2010, 12:26
joe_peters joe_peters is offline
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Re: Crank, no start; fuel pump not priming?

Ok.

Renix, B Latch relay instead of ASD relay, essentially the same function. B Latch relay provides 12 volt power to the coil on the 3-wire connector at the ICM, pin "A", pin "B" is ground, pin "C" is tach. Check for pin "A" 12 volts and pin "B" ground. The B Latch relay also provides 12 volts to the fuel pump, bypassing the ballast resistor, when the key is turned to ON. After 3-seconds, when the ECU has received no signal from the crank sensor, the ECU cuts the ground to the B Latch relay and cuts off the fuel pump. Before we go any further, GROUNDS are CRITICAL to the Renix system. Three extremely important system grounds are at the DIPSTICK TUBE--the ICM, the ECU, and the o2 sensor. Clean down to bare metal, treat with anti-corrosive agent, make the connections TIGHT. Also, there is one and one only unibody ground--the POS braided strap from the head to the firewall. Replace with a 4 or 2 gauge cable, strip the surfaces to bare metal, anti-corrosive agent, and make the connections TIGHT. Now would be a good time to talk about the ICM to coil clips--they corrode overtime and need to be cleaned and treated with dielectric grease.

Ok. The 3-second prime is from the B latch relay bypassing the ballast resistor. Once the key is turned to START the 12 volts to the fuel pump is provided by the starter relay, again bypassing the ballast resistor. Once the engine starts, and is running at idle and all the way up to just short of WOT, the fuel pump relay sends 12 volts to the ballast resistor on the driver's side fenderwell--white ceramic piece, two wires--and then 6 volts runs to the fuel pump. You can jumper the two wires together eliminating the ballast resistor. The pump might be a little noisier. When the engine is running at WOT, 12 volts is sent to the fuel pump bypassing the ballast resistor, from the oxygen heater relay.

Cranks, won't start questions to be answered:

Is there spark?

Is there spark to ALL cylinders--is the rotor turning?

What is the spark's condition--blue and snappy (good), or yellow and weak (not good)?

Is the fuel pump running?

Is the fuel pressure correct?

Is there a firing impulse to the fuel injectors?

Do you have spark, and is it going to all cylinders? If yes, go to fuel. If not determine what needs repaired.

Is the fuel pump running? Yes, then test pressure. If pressure is good, then test for firing impulse.

Fuel, air, compression, spark, all in the right quantities, at the right time, in the right place.

Post back what you find.
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Old July 7th, 2010, 14:25
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Re: Crank, no start; fuel pump not priming?

Quote:
Originally Posted by joe_peters View Post
Is the fuel pump running?
NO.

Grounds are good.

Tracked down the fuel pump relay with FrankZ on the phone. When key is turned to on, I could hear and feel the relay clicking. 12v @ pin #30. Jumped 30 to 87, and no noise from the fuel pump.

Finally got fuel pump changed. Still nothing from pump with key ON. Crank, no start.

Well, at least it's raining again
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  #10  
Old July 7th, 2010, 14:37
joe_peters joe_peters is offline
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Re: Crank, no start; fuel pump not priming?

Ok, key on ENGINE running you will have power from the fuel pump relay.

Your engine is not running, you need to find out why there is no power from the B Latch relay for the 3-second prime, and you need to find out if there is power to the pump when CRANKING, and that is from the starter relay.

If you don't have the power from the B Latch relay, or from the starter relay, getting to the pump you have an open circuit someplace.

Hook up a test light to the pump power feed. Have a second set of hands turn the key to ON--no light, FUBAR'd B Latch relay circuit. Ok, now have the second set of hands crank the engine over using the key in the START position--no light, FUBAR'd in the starter relay circuit.

Again, you have four separate and distinct ways that power is delivered to the fuel pump. If you have no 3-second prime, but you have power to the coil and spark, then it should still start when you go to START as there will be power through the starter relay, it will just take a longer time to crank before it starts.

Again, the fuel pump relay doesn't come into play until the engine is running and the key is back in the ON position.
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  #11  
Old July 7th, 2010, 14:58
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Re: Crank, no start; fuel pump not priming?

B Latch relay = Power Latch relay? 3rd one from battery, fuel second back?

I have key on power at both. Nobody around to crank while I look.
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  #12  
Old July 7th, 2010, 15:35
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Re: Crank, no start; fuel pump not priming?

Correction:

Fuel pump relay; constant power at 30. Key on power at 30 and 86.
B Latch; no constant power. Key on power at 86.
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  #13  
Old July 7th, 2010, 16:29
Shorty Shorty is offline
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Re: Crank, no start; fuel pump not priming?

absolutely no clue where the B+ Latch Relay receives power (but I'll go look), but you need power to "30" for it to function.

While I go look, try running a jumper from battery positive to the "87" terminal and verify the pump now runs.
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Old July 7th, 2010, 16:32
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Re: Crank, no start; fuel pump not priming?

Quote:
Originally Posted by kujito View Post
B Latch relay = Power Latch relay?.
yes- proper name is B+ Latch Relay-- B+ stands for "battery positive" which translates to "battery power" or Power Latch Relay.
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Old July 7th, 2010, 16:36
Shorty Shorty is offline
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Re: Crank, no start; fuel pump not priming?

B+ Latch Relay should be powered by a red wire that is fed from the starter relay (metal box off battery) through an orange fuse link.

orange fuse link appears to come directly off the same terminal that the battery cable is connected to-- I guess it's time to stop monkey-dorking around with the wiring diagram and go look at mine--

back in a flash.......
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Last edited by Shorty; July 7th, 2010 at 16:42.
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