not a good morning - fuel pump??

PaxtonShelby

Registered User
Hi all. My 90 SC auto died on the way to work this morning. It has 135k on it. Prior owner had tranny rebuilt, head gaskets replaced, water pump, ABS computer / master cylinder assembly replaced, and other small items - all within the last 18 months / 3000 miles.

I was 1/2 way on my 6 mile commute when there was a bucking / surge in the power, then she just died. This had happened a few times in the last month, each time under very VERY light throttle. ( The bucking / surging, that is, not the dying part. Today is the first time she shut off on me.)

This time she would turn over, but would not restart. When I turned the key to the first on position, I did not hear the fuel pump kick on like my Mustang GT used to do, so I'm thinking ( hoping ) that the fuel pump might have gone bad. I'm new to the SC world, so any help / suggestions you can offer would be greatly appreciated. Car is currently at my local garage where it will probably sit until Fri / Sat when he has time to work on it.

I checked the inertia switch in the trunk and it was still in the normal "ON" position, so that isn't the problem.

If you feel it is the fuel pump, should I upgrade the capacity of the pump or stay away from any particular brands of replacement pumps?

Thanks in advance for the help folks. I am eagerly awaiting your diagnosis!

Ron
 
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I don't have my 90 XR7 any more but I will try to remember some things that went wrong and how I fixed them. First, take a tire pressure gauge and check your fuel pressure at the schrader valve with the key ON. Should be about 35 to 40 Lbs.. If you have fuel pressure and it still will not start, could be the coil. Seems I had similar issue. Lite throttle and it would cut out or miss. Removed coil and it was puking white stuff underneth. Also, if you have a 5 speed, with the key on and the upshift lite stays on, then it is probable a crank position sensor. The day I got my XR& I was just driving along and the car died like I turned the key off and immediately the upshift lite came on. If they are OK, then I would look at the DIS module on top of the A/C compressor. Pull a spark plug wire off and check for fire. No fire probably means DIS is bad.

Hope this helps!

Ed

’94 SC Red Auto: 110,000 Miles, Headers, No Cats, Pro Torque 2500 Stall Converter, TRANSGO Shift Kit, 10,000 Lbs Auxiliary Tranny Cooler, Tranny Fluid Temp Gauge, 3.73 Gears, 70mm BK Throttle Body, 76mm C&L MAF with Gold Tube, A/F Ratio Gauge, Raised SC Top, Teflon IC Seals, ’90 XR7 SC Pulley, ARP Head-Rod-Main Studs, Scorpion 1.73 Roller Rockers, Solid Motor Mounts, Iridium Plugs, Live Wire Plug Wires, Screamin’ Demon Coil, 36# Accel FIs, Custom Air intake, K&N 9” Cone, Royal Purple Synthetic Lubricants and Optima Yellow Top.
 
Ed - thanks for those tips. My car is an auto, but I noticed that the upshift light came on while I was coasting to a stop. At least I thought it was an upshift light - an amber colored upward pointing arrow below the gauges on the right side of the steering column??? I thought it was odd to see such a light on an auto-equipped car. My mechanic is already checking the fuel pressure, & I'll tell him about the coil and crank position sensor possibilities. The DIS module was also recently replaced prior to me buying the car in February, so hopefully that's ok. Is there a diagnostic check I can run to point me in the right direction?

Thanks again for the help Ed - those are very good points you made. I really appreciate it. The SC needs new tires and I have a set of nice SVT rims ready to go on it, so I'm hoping this fix doesn't set me back too much $$$ - I want to buy the new tires and put on the new shoes!! :D

Anyone else have thoughts / opinions on my dilemna?
 
If the upshift light was coming on, I believe that's the crank sensor. May also double check the Harmonic Balancer is in one piece. If you don't hear the fuel pump, may check the fuel pressure at the rail after you turn the key on. It could be on the verge of dieing.

-Melon
 
Ed - thanks for those tips. My car is an auto, but I noticed that the upshift light came on while I was coasting to a stop. At least I thought it was an upshift light - an amber colored upward pointing arrow below the gauges on the right side of the steering column??? I thought it was odd to see such a light on an auto-equipped car. My mechanic is already checking the fuel pressure, & I'll tell him about the coil and crank position sensor possibilities. The DIS module was also recently replaced prior to me buying the car in February, so hopefully that's ok. Is there a diagnostic check I can run to point me in the right direction?

Thanks again for the help Ed - those are very good points you made. I really appreciate it. The SC needs new tires and I have a set of nice SVT rims ready to go on it, so I'm hoping this fix doesn't set me back too much $$$ - I want to buy the new tires and put on the new shoes!! :D

Anyone else have thoughts / opinions on my dilemna?

You are welcome!

If the upshift lite came on and stayed on even while cranking, then it is the crank position sensor. That is the only thing that amber lite is good for.

ED
 
Fellas, his car died.
If I recall isnt it on if the car dies?
I dont recall him saying it was on while he cranked it.
Id go for fuel/ignition problems.

Crank is a good idea too
 
I can't remember if the upshift light was on only after the car stalled and I was coasting to a stop, or if it also came on when I was cranking the engine trying to start it back up. Thanks for the tip though - I passed it along to my mechanic, along with the other pointers. Thanks fellas. If you think of anything else, please let me know.

If the problem is a crank position sensor, is that a big $ part to replace? There's a lot going on in the front of that motor - wondering if a lot of labor will be involved.
 
Skip worrying about the crank sensor until you check fuel pressure. When the key is on and the engine dies, just about everything lights up. That's just how it works.

once you are sure that you have fuel pressure, and the car still won't start, then bother looking to see if the upshift light is on during cranking.

You could try to lay under the car and hit the fuel tank good and hard. sometimes that will let a fuel pump start to work again until the next time you shut it off. That can get you home at least.
 
Thanks for the info Mike. I was going to bang on the tank, but I figured I'd let the mechanic do that as part of his "diagnosis" :) He's going to check the fuel pressure first. I hope that's it ( pump ). I couldn't hear the pump running when I turned the key to the first position. What sucks is that the tank is F U L L!!

Question about the harmonic balancer. There are lots of threads here that talk about it. Talk about the main bolt shearing off and the pulley bolts breaking ( had that happen on my supercharged '66 Mustang ). Would the car not restart if the balancer is moving ( front to back, or wobbling )? If so, is that because the crank position sensor ( it is behind the HB, right? ) is either damaged from contact with the HB, or because the balancer has "spun" and the CPS is no longer getting an accurate reading, preventing the engine from firing at the proper time?

If the CPS is bad, can it be replaced without removing the HB? From what I've read, it sounds like once you take a stock HB off of the car you should pretty much throw it away, especially in my case where the car has 135k on it.

If my HB is not the problem, is there any harm in replacing the main HB crank bolt and the ( 4? ) pulley mounting bolts? If these things are prone to failure it seems like it might be worth doing. I drive this car pretty gently and don't really want to spend the $$ on a BHJ HB at this time if it isn't absolutely necessary.

Thanks again everyone - I really appreciate your ongoing help on this. :)
 
Yes, you can replace the crank sensor without removing the HB,
Id just make sure the crank bolt is torqued down.. it goes to the old thing "if the part aint broke dont fix it"


-Tony
 
Those bolts only fail if you don't catch the balancer moving before they can fail. It depends on how much clearance was on the original crank sensor for how much movement the balancer can have before the sensor is damaged.

If the balancer isn't moving now, there isn't any reason to think the bolts are worn out Both the vane and the main pulley are bolted to the center hub of the balancer. Thus other than the outer ring no longer dampening anything that itself won't make things out of time.

It's just a question of the vane moving back and forth which is bolted to the back of the balancer whacking the crank sensor causing it to fail, or moving so much off the end of the crank that the sensor no longer reads the vane.
 
no, there is a sensor ring bolted to the back of the harmonic balancer

-Tony

On the very back, got it...with bolts that come in from the rear or...? How many pieces total (stock assembly), not counting the crank itself?

Thanks Tony

Ken
 
on the very back of it there is a "sensor ring" bolted to it, its the harmoic balancer + the sensor ring, and two bolts from the back holding it in
 
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