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Discussion Starter #1
I have a 1997 Thunderbird 4.6L V8, 225,000 miles. Was running great and now engine wont start. Battery is strong and turns over engine nice and fast but it doesn't fire at all. Not even a partial ignition. I checked the spark and its good. I assume this means it must be fuel related. Not sure what could cause a sudden no fuel problem or how to go about testing whatever could be the problem. Maybe the fuel pump (hope not)?
I'd love to get some guidance on what can cause this and the test process. Don't want to just start buying parts. I hope someone can help and thanks for reading.
 

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Could be fuel related, there are a few easy things you can do to start ruling things out.

First thing - put the ignition into run after off; you should hear the fuel pump run for a couple seconds along with a few relay clicks. If you hear the pump, check the schrader valve on the fuel rail for pressure (be careful if you depress it without a fuel pressure gauge). If you have pressure, it should be upwards of 38-40 PSI and is probably not a fuel system issue. If it's significantly less, you can reprime the system to see if it pumps up to the right pressure by cycling the ignition from off to run several times. If this is the case, it could be a weak pump and/or bad pressure regulator.

If the pump is indeed dead, it could be electrical or mechanical. The CCRM has the fuel pump relay in it, so you can probe the connector for voltage to the pump without having to drop the tank to access the pump and connector.
 

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Before doing any of that, open the trunk and look on the left side, and you will see a little red button tucked behind the carpet. Push that red button. If it clicks down, then that means the inertia switch was tripped, which is designed to cut off fuel in the event of an accident, and afterwards, cycle the key on and off a few times without cranking the engine to prime the fuel system, and it should start right up. If that switch isn't tripped, then proceed according to terminator's post.
 

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Discussion Starter #4
Thanks for the responses. My son has the car about five hours from me and I’m having him do the tests. Inertial button is not triggered. I tried to have him listen to the pump hum after turning ignition on (KOEO) but the answer is not definitive. He said he heard what might have been a hum but it lasted a maximum of one second and was sandwiched between clicks on both sides. At the gas filler tube with the cap off, the sound was even lower. Seems to me it should be louder at the filler tube and it should last longer than one second. I’ve never found it hard to hear if you’re listening inside the car. Next step is to check the fuse box and if all is good borrow a pressure meter and do a formal pressure test at the Schrader valve. No results on that yet.
A few questions:
1) Terminator: Are you sure the fuel pump relay is in the ccrm? Actually, in my car Rock Auto calls this the “Body Control Module” or (BCM). They also show a “fuel pump circuit opening relay.” Is this relay what energizes the pump or ??? If it does energize the fuel pump is it possible this relay is inside the BCM as a replaceable part?
2) Does anyone know how to find out what terminal on what box or relay powers the fuel pump on this car so I can probe to check for volts?
3) There are no OBD2 codes seen. Is this expected if fuel pressure is gone?
4) Is there any relay or voltage that can be tested that would keep all injectors from operating? If so, I should test that as well since it could keep fuel from reaching the cylinders.
Any other suggestions?
Thanks for your help and thanks for reading.
 

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BCM is a GM term, so RockAuto's information is hereby considered invalid. :tongue:

The PCM (to the right of the glove box) energizes the relay which is in the CCRM (located under the radiator core support near the pass. headlight). Pin 5 (PK/BK) powers the fuel pump from the CCRM relay when it is energized by the PCM (on pin 11 - BK/Y). The ground feeds to the ground bus inside the pass. kick panel, near the door lamp courtesy switch.

You're not likely to get a trouble code for a condition the PCM can't monitor. It only will throw a code as a result of particular emissions or other test being run, then failing - which requires the engine to be running.

The injectors are wired directly to the PCM, so it's probably not an injector issue. The earlier 4.6 car (94/95) PCMs tend to be notorious for hanging an injector open, but otherwise there's not much talk about them failing to fire.

A couple other thoughts. Measuring for voltage from the CCRM is a quick way to tell if electrical issues are the cause (by not getting voltage on the +12V feed pin) but it's not a a surefire way to rule them out either. The feed has to run all the way from the CCRM at the front of the car through the body harness channel up under the passenger seat to the pump, along which there are a number of connection points which could also be causing issues. The only surefire way to tell if the pump is indeed getting voltage is to drop the tank and probe the connector to the pump on the tank. If I had to take a wild guess, the pump is probably shot (based on my experiences with no fuel pressure in the last several years) - but with the simple tests, checking fuel pressure is next on the list. :)
 

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Discussion Starter #6
Thanks Terminator for your help and information with this. Looks like I’ve got the right guy on the job! What you’ve said all makes good sense to me. I’m crossing my fingers it’s not the fuel pump but I also agree it’s probably most likely. If it’s the pump, it may be the last stop for the car.:crying: I think I can fix all else DIY style. My thought was to:
1) Verify 12v at the output side of the inertial switch. I assume this will be present only for a few seconds after KOEO (does it turn back on when the engine is cranked??). If present, verify no fuel pressure at the Schrader valve and if no pressure, assume it’s the pump since I’m not planning to drop the tank to dig deeper.
2) If no or low 12 volts at the output side of the inertial switch, work back to the CCRM pins 5 and 11 to identify where it’s missing.
Questions:
1) When measuring volts at the inertial switch can I ground the voltmeter to the body of the car? Not sure what better ground is in that area.
2) I attached a screen shot of the "opening relay" at Rock. What is it for? Is Rock just confused and its not for my car?
Let me know if you think I’ve overlooked something and thanks much! :smile2:
 

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Yeah, the FP should come back on during cranking. Any point on the chassis should be fine as a ground.

As far as that relay... It has a 1991 part number, but I've never seen such a thing on my car. It's not in the fuel pump wiring diagrams either.

 

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Early tbirds had a fuel pump relay -- I think it was mounted in the trunk next to the intertial switch but i don't recall 100% as it's been a long time since I gutted my 93 donor car and swapped parts into my 95 car.

Later tbirds (94-97) had a CCRM (a module behind the front passenger headlight that contained relays for the fuel pump and a few other things like the radiator fan IIRC).

Relays can go out. Generally though, they get stuck (like in an off or on position) or a solder joint breaks internally and it never energizes. If you hear it pumping and then stop, I'm not sure if's the relay.

One way to confirm that its' the pump is check for fuel pressure. AZ rent-a-tool offers a fuel pressure test that you can hood up to the shrader valve (the thing that looks like a bike tire nipple) on the fuel rail. See what pressure if builds to.
 

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I'll confess, I did this ^^^ to the Mark VIII too when the pump died in it 2-1/2 years ago. It gets a lot of hate on here when done, but there have been no ill side effects of my having done so. No gas smell, no additional road noise, no "extra" body flex, and 50,000 miles on the new pump. :D :rolleyes:
 

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It takes two people to confirm the fuel pump is or isn't running - one inside the car turning the key on, and one under the car in front of the passenger rear tire listening.

Would be good to do that before just tearing into the car (literally). Also turn the HVAC off first.

This also could be the crankshaft position sensor. Same symptoms, though sometimes the car will start and run fine, then next time might not start. The symptom is if the tach doesn't move at all while cranking it.

Al
 

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This also could be the crankshaft position sensor. Same symptoms, though sometimes the car will start and run fine, then next time might not start. The symptom is if the tach doesn't move at all while cranking it.
True, this is also a fairly common cause of no-start conditions on these. I had considered mentioning this as well, but he mentioned he had spark earlier so I decided it was a less likely culprit. True though, it can be intermittent. One way to know immediately if this is a likely factor while trying to start - if the service engine soon light stays on when cranking, it means the PCM is not getting signal from the CKPS.
 

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Discussion Starter #13 (Edited)
My thanks to all for the great info provided with the latest replies. My son measured the 12 volts at the output side of the inertial switch (used the switch mounting screw for ground). He measured 12v for ~2secs after KOEO. This should rule out the electrical system, ccrm wiring and related. As terminator points out, my son tested good spark earlier while cranking. I assume this rules out the crank position sensor but let me know if it’s not that simple. While it seems increasingly clear the fuel pump is all that is left, I still plan to test for fuel pressure with KOEO in the next few days (need to get over to Auto Zone).
Question: I was also going to check the fuel pressure regulator for leakage at the vacuum port. If none, can I assume the FPR is not at fault? Remember, the engine does not even flirt with firing or stumbling. It just cranks.
Here is some history I didn’t mention earlier:
1) Over the past 5 years or so, there has been 3-4 instances where the car would crank and not start. After a second or third attempt or a little rest, it started right up normally.
2) Also, over the past several years I’ve noticed the speedometer stays at zero mph after startup. Once underway it starts working but sometimes becomes intermittent even underway. I don’t recall any tachometer anomalies.
I have been warming up to gunn’s idea to create an access hole in the trunk. No Tbrd should be without one!:grin2: I have tin snips, the grinder in the attached picture and a good Dremel tool. I wonder if the right attachment on the Dremel would make this easy?
Question:
1) I can’t tell from the pictures gunn included exactly how to place the access door on top of the fuel pump. Does anybody have any dimensioning or positioning information for the access hole on a 4.6L 1997 LX?? I’m sure if I go in there and pic a good spot, I’ll be wrong and end up with an embarrassing mess! :surprise:
2) I also can’t tell how to RR the pump. Doesn’t look like it screws in. What tools do I need? What do I need to RR the gas tubes from the pump?
3) I also attached a picture of the fuel pumps offered by Rock. Any comments about which would be a good bet?
Thanks again to all.
 

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I get the impression that you didn't test the crankshaft position sensor as if you're determined that the problem is the fuel pump, so I will say it again. Crank the engine and see if the check engine light is illuminated while cranking. If it is, it is bad. If not, THEN look at other things.

When you say 3-4 times the car didn't start, do you mean not at all, or did it start after about 5 seconds? These fuel pumps can have an issue where the fuel drains back to the tank, and have "long cranking" times to start it. If you turn the key on for a couple seconds to prime it, then it starts right up, then the fuel pump is getting old.

I would rather pay someone $700 to install a fuel pump or spend 14 hrs killing myself under the car myself before I cut a hole in my car. You might miss the spot or hit the fuel tank. Also, everything has to be installed just right, or you will be taking it back out again. You really need experience for that job, even to cut the access hole.

Only the right side of the tank needs to drop down to access the pump. Granted, it is much easier on a lift. That's why I had RobertP install a fuel pump in my old 95 T-Bird. Take it to a mechanic.

Al
 

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If you do cut the access panel with the angle grinder with the tank in place, please have someone get a video.

From a distance...

:smile2:
 

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It'll be an embarrising mess no matter what. Sorry, but it's one thing do this to a Lemons car or a rusted out beater, but anything else it's just lazy and half assed. Dropping the tank is not that difficult, a fuel pump will last a hundred thousand + miles with no service, and for the couple hours saved you're forever left with a big ass hole in the floor.
 

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Discussion Starter #17
Measured the fuel pressure at zero. The pressure gage needle Didn’t move with KOEO. Also tried T6Rocket’s suggestion and the check engine lite did turn off when cranked. I think we can say it’s the pump. It’s getting 12v and its giving zero pressure. The car is on the street 5 hours from here. I don’t expect to keep it for more than 6-12 months and it has 225K miles on it. Not wild about taking the Makita to it but ‘major-surgery’ is pretty much the last hope. Right now, I need to nail down the location of the fuel pump so I know where to cut.
Question:
In post #9, S4gunn said he “removed the trunk and cut an access hole.” Is this on a T-brd? I’ve not heard that you can get to the pump thru the floor of the trunk. Most pictures I’ve seen sort of look like it’s under the rear seat, passenger side towards the front part of the seat (really the floor under the seat). Others look like it might be the same but on the driver side. In S4gunn’s picture I don’t even see the fuel pump thru the access hole. If anyone has done this on a 97 TBrd or same generation please share information about where to place the access hole.
Thanks much for all the comments, thoughts and guidance.
 

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Yes, it's under the passenger seat. If you remove it (push it back and down to unlock, then lift it up and out as it comes forward) and lift the sound padding you will see on the passenger side where the wire goes through the floor to the pump. If you are looking towards the rear of the car, it's immediately to the right of the "hump" (if your car has the hump it's actually more or less centered where the right side of the hump ends), a couple inches left of where the wire goes through. Check the link to the other thread in Gunn's post for a better photo of location.

The pump has a circular ring that rotates to unlock it. There's a rubber gasket between the tank and the pump assembly hat. If you have more than 3/4 tank of fuel you may want to try and drain some before removing the pump, since the hole in the tank isn't at the very top.

Be careful how you slice. You don't want anything that will spark (for obvious reasons), and there's only an inch or so of clearance between the floor and top of the tank. IIRC I just used tin snips starting from the hole for the pump wires. I didn't remove the metal, but folded it back so I could push it back in place. I sealed the cuts as a moisture barrier. With the seat and sound padding back in place, there is no evidence of an access panel at all, contrary to some comments.

I understand the motive for going the "quick and easy" route. In my case I was unable to drain the tank with the tools I had available, the exhaust wasn't coming down (therefore making it impossible to access the pump assembly even when I attempted to drop the tank) and I needed the repair done ASAP (no way I could have afforded paying someone else $$$$ to do it at the time). Also factors were the fact that the pump died in the middle of winter during the work week and I don't drive my other car at that time of the year - so every day the car was down was PTO used up at work. Hence my decision to take the much hated path of cutting a hole in the unibody. :rolleyes:
 

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Don't cut a hole in the floor. To replace the pump, you don't have to remove the tank completely, you can get away with just lowering it down some, and by the time you remove the rear seat, cut the hole in the floor, and make the access panel, you will probably spend just as much time to hack the car up as you would to do it right. Here's how I do the fuel pumps on these cars.
-Raise the vehicle up.
-Remove the small cross-brace that goes under the exhaust right in front of the tank, 4 8mm bolts
-Unhook the rubber exhaust hangers at the mufflers, rear diff, and at the left side of the tank, and let the exhaust hang down. No need to unbolt the exhaust from the motor
-Unplug the gray connector going to the fuel pump at the right front of the tank
-Unclip the fuel lines to give them slack
-Unbolt the right side fuel tank strap and put a jack under that side of the tank
-Unbolt the left side fuel tank strap and put a jack stand under that side
-Lower the jack and pull down the right side of the fuel tank. You will now be able to see the fuel pump, and will have just enough room to get it out.
-Put the new pump in, along with the new rubber O-ring, and re-assemble in reverse order

This whole job, on the ground, and with hand tools should take more than 2-3 hours if you've never done it before. On a lift with air tools, I can do it in under an hour.
 

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Discussion Starter #20
Madmicky: Thanks for these details. This is great information and I’m sure this is a very sound approach. For now, trust me, there are equally sound reasons I’m not getting under the car.

Terminator: Thanks for your description. I think it makes sense if I properly understand what you’ve said. I haven’t been in there yet but will be soon. I don’t understand your reference to the hump. Is this the hump for the drive shaft? For reference, I attached a picture from gunn’s post (pic1). Also, here is a link to a description of the job by Fastfreddie:
http://www.eastcoastrollingthunder.com/smf/index.php?topic=1016.0
His description is a little convoluted but combined with pic1 and pic2 and your description here is what I’m deriving from it all:
In pic 1, I assume I’m heading towards the rear of the car in going from lower right to upper left corner of the pic. With that in mind, the cutout I think is positioned between the grommet (on the right as you face the rear of the car) and the passenger side rear seat fastener/bracket where the rear seat attaches. Further, the front edge of the cutout, opposite the flap is probably about positioned under the front edge of the rear seat. This all seems consistent with pic2 where you can see the seat fastener/bracket at the front left of the white cover (as you face the rear of the car) and the grommet on the front right side of the white cover.
Question:
  1. Am I looking at this correctly? If so, where does the “hump” you mentioned come into this? I don’t see a hump in these pictures.
  2. What did you use to “seal the cuts?” How did you rejoin the cuts? Screws?
  3. Are any special tools needed to RR the rubber gas lines from the pump’s gas tubes? Might the rubber gas lines need to be replaced?
 

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