tach jumping and hard start

derekhay316

Registered User
For a while now my 89 sc has occasionally had hard starts and engine drops and just yesterday I came to a red light and noticed the tach jumping from 2500 rpms to 500 rpms. It wasn't just the gauge the engine was actually sputtering along with it. As I got above 2000 rpm the car seemed normal with some engine blips. Anyways I figure it could be the cam sensor or fuel pump (my pump is whining and is on its last legs). I replaced my crank sensor and dis a couple of months ago so It wouldn't be that. What do you guys think??? THanks.
 
Ok well I just got back from replacing the cam sensor and its a no go still. The car turns over but just won't start. I have replaced the crank sensor and dis in the last 3000 miles so I doubt it would be those. All I can think of is the fuel pump. The pump has been whining (about to kick the bucket) for the last year. The pump does turn on when I turn the key on though. I can hear it turn on and then turn off while turning the key. Could it be a possibility that the pump is barely pumping gas and needs to be replaced??? What do you guys think?
 
Keep trying!

Keep trying to start your car. Mine did the same thing after I put a new cam sensor in. Took about 5 tries till it started.
 
I put the cam sensor in and tried about 3 times to start it. And I just tried another 3 times to start it and it turns over it just won't start. It seems like every once and a while it is just about to start but it doesn't.
 
Nope. I came to a red light and looked at the tach and it was jumping from 1500 to 500 rpms. Road really sputtery all the way to my gf's house. I tried starting it an hour later and it wouldn't start. Then i changed the cam sensor and still the same.
 
Did your check engine light come on when it started doing that?

Another thing to check would be the fuel pressure at the fuel rail with the key on. You might not be getting adequate fuel, either due to the pump, filter, etc.

-Rod
 
FUEL PUMP

A loud pump is a soon to be bad pump . Get the 255 type pump , around 110 bucks on E-Bay . DW
 
derekhay316 said:
How do you do the fuel test???

Hook up a fuel pressure gauge to the schreader valve on your fuel rail, and see what pressure you're getting with the key turned on.

-Rod
 
The fuel rail is the metal line that your fuel injectors connect to. The schreader valve is just like a tire valve stem, it is welded onto the fuel rail. You screw the fuel pressure gauge onto that valve to determine how much fuel pressure you have at the rail.

-Rod
 
Once again, that will only tell you that SOME fuel is flowing, it will not tell you HOW MUCH PRESSURE you have at the rail.

-Rod
 
derekhay316 said:
Couldn't I just unook the fuel line, put that into a bucket and turn over the engine to see if any gas comes out???
Sure, its rather messy, but maybe you can rig somthing up to catch most of the gas. Also, when you first turn the key to the run position, the pump should turn on for a few seconds. You don't even need to start the engine. Like racecougar said though, you won't know how much pressure you're getting. But if its moving gasoline so fast that you are inclined to shut it off quickly, chances are its working just fine.
 
Same thing sorta
Replaced Cam,Crank and almost Every other sensor before i found out the stupid Cam stator wasent in properly.
After 2 months of waiting she fired up like the day she was bought.
 
fuel pressure test

no , you cannot just unhook the fuel line and run it into a bucket. First of all, exactly where are you gonna disconnect it? if you do this where the fuel filter goes, you are bypassing the injectors and Fuel pressure regulator, so you still wont know if they are the culprits. also you will just get gas flow , you still won't know the pressure. Get a fuel pressure tester (napa has one for about 45 bucks that will work on Ford, GM, and Chrysler.....i lost the part number , sorry) and screw it on the thing that looks like a tire valve on the fuel rail. the pressure should come up to around 38 lbs or so with key on, and should stay there after the pump quits running. if it does not hold pressure then you have a bad pump or Fuel pressure regulator. usually (not always...) pressure too low means bad pump, pressure too high means bad regulator. but if the regulator is letting all the fuel return to the tank then you have no fuel pressure....it just seems like the ford FPR usually causes too much pressure when it fails.....
 
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