: Tricks to Change Fuel Pump 97 STS??



macx
05-02-04, 12:20 PM
Found I have low fuel pressure -
reason it's recently been starting hard
and intermittently losing power and
sometimes stalling.

Put my fuel pressure gauge on,
found 20 to 28 at idle, not over
30 with the vac pulled off the reg.
And the needle not only bounces,
the pressure varies up and down
several pounds.

When revving it up, sometimes drops
under 20 and bogs - and that's not
in gear!

Already put in the new fp relay and
regulator - at least THOSE are easy
to change! (about the only thing
on this car yet that's been made
easy to do! - and I've done WAY
too much fixing for a "premium" car!!)

Anyway - I have changed in tank
pumps before, just not on this model.

Any special watch-outs or tricks to
make it less difficult?

Appreciated!

Logandiagnostic
05-02-04, 01:47 PM
Pumps wear out. They dont last for forever. Any car.

The GM products have a specfic problem to check for. While the tank is out check the inner tank wire harness.

When the pumps wear, they can start drawing some extra current. This can cause the inner tank harness to get hot, and 'blue' the harness connector terminals.

'Blued' terminals can cause intermitant starts or no starts.

Be sure to unplug and inspect the inner tank upper harness connection. It may save you from dropping the tank a second time.

Logan
www.airbagcrash.com
www.logandiagnostic.com

macx
05-02-04, 02:33 PM
Really appreciate that!

I routinely check and clean up terminals
when I've got things apart - I take it cleaning
up the blued ones will correct this problem?

Thanks again!

I know fuel pumps wear out - I've replaced
on 2 other of my cars before. It just seems
that a greater number of items that always
cost more than the same parts on competitive makes
has worn out on this car much more quickly than
on other cars I've had, even cheaper makes.
I've got an 89 Lincoln Mark VII LSC that I use for
work with 220k miles that I've had LOTS fewer and
lots less expensive problems on than with this car
that has about 1/2 the miles. My wife had a similar
LSC with hi miles that also had very few problems.

We love the car, it's just been a PITA and very costly
to keep running - one always difficult to work on and expensive
major part after another has been failing over the last 25k miles.
Not to mention the oil pan leak. And knock on wood the
head bolt/gasket problem hasn't hit us. Seems a company
with the past reputation of Cadillac would at least stand
behind things like the pan leak and head bolt problem just
to maintain their customer loyalty and reputation - and for
darn sure do something to remedy the problems within a
short time of them being discovered on new models (like
the Northstar problems) instead of allowing them to continue
over a period of several years of subsequent production.

I'll likely never buy another Cad just because of my
experience with this one and the many posts I've read
from far too many people with the same problems.
It's a real shame - the design and technology are
great, the car is beautiful, and drives and rides
like one would expect a premium car to do.

Randy_W
05-02-04, 06:04 PM
Macx, if you ever read the list of recalls and problems associated with Ford OHC engines, you would be glad you have a Caddy! At least Cadillac never had to recall an engine for putting out less than the advertised H.P. like Ford did with the late '90's Cobra engines. That is basically the same engine used in the MK VIII. They have piston slap issues, oil leakage, piston failure, etc... Nothing is perfect, if you got a lemon, it's just bad luck!;)

BeelzeBob
05-02-04, 06:13 PM
As Logan says double and triple check the harness and terminals for melting and heat damage. Very frequently the harness and terminals and connectors inside the tank AND at the chassis end of the in-tank harness are damaged when a pump starts to fail. If a wire looks melted or anything like that at all replace it....don't just clean it up.


Fuel pumps are most frequently damaged by the owner putting gas treatments/injector cleaners/fuel system cleaners/etc. into the tank with the fuel. The fuel ciculates thru the pump and directly around the windings of the armature to cool the pump motor....and the harsh solvents in the cleaners will eat the insulation off the armature windings and cause them to short out and the pump to loose power...and draw more current and melt the harness. Almost every fuel pump returned from the field that I have examined over the years had this problem.

OlManRivah
05-02-04, 06:37 PM
Interesting comment BB.....

I , personally, don't put any additives in my Northstar. Aluminum fear factor I guess, lol. But, I routinely put injector cleaner in my other engines, from time to time, with no problems.

Would you like to dwell on this a little more, maybe, in a new thread?:)

BeelzeBob
05-02-04, 09:51 PM
What's there to dwell on...??? The gasoline flows thru the fuel pump and contacts the windings on the armature. The harsh solvents in many cleaners and additives will eat the insulation off the windings and the pump armature shorts out. Happens all the time. Worst case is the guy that lets the tank get low and adds a whole can of the stuff to the nearly empty tank and then drives to the station to fill up....in the meantime the pump is circulatint the strong, undiluted solvent and damages the pump. It may show up soon or later... Use of additives is really not recommended. There is really no need for them on a continuing basis.... If you do feel the need put in the correct amount into a full tank or put it in at the station as you are filling up so the pump doesn't see the strong solvent.

This has been covered quite a few times in the past. Try searching the archives to see what pops up.

I have done post mortems on a lot of electric fuel pumps returned from the field over the years and the vast majority of them are failed due to solvent damage.....same with injectors.

OlManRivah
05-02-04, 10:46 PM
What's there to dwell on...??? The gasoline flows thru the fuel pump and contacts the windings on the armature. The harsh solvents in many cleaners and additives will eat the insulation off the windings and the pump armature shorts out. Happens all the time. Worst case is the guy that lets the tank get low and adds a whole can of the stuff to the nearly empty tank and then drives to the station to fill up....in the meantime the pump is circulatint the strong, undiluted solvent and damages the pump. It may show up soon or later... Use of additives is really not recommended. There is really no need for them on a continuing basis.... If you do feel the need put in the correct amount into a full tank or put it in at the station as you are filling up so the pump doesn't see the strong solvent.

This has been covered quite a few times in the past. Try searching the archives to see what pops up.

I have done post mortems on a lot of electric fuel pumps returned from the field over the years and the vast majority of them are failed due to solvent damage.....same with injectors.
OK, I'll be the Devil's Advocate...
Dwelling........

1) What proof do you have it's the additive and not an inferior winding insulation? GM, like other manufacturers, make mistakes. It's called a recall.
2) Try the search on an additive based Forum for different results. Some additives are recommended. (Mopar and it's CCC for Carbon cleaning for example. Auto-rx by many)
3) Any valid statistics on Fuel pump failure on additive users vs non-users?
4) Any valid statistics on cost of Pre-ignition damage vs Fuel pump replacement every 100,000 miles.
5) Any valid statistics on how many oz's of additive it takes to destroy a fuel pump, if it does?

Not bad, for a guy that doesn't use it in his N*, huh!
I'm going to try the Auto-rx treatment on my Toyota 4x4 w/360k to salvage the seals that are beginning to emit the puff of smoke at start up. It will be my first serious use of an additive.

I did like the bit about adding a can of additive and then going to the pump.
Maybe it's shock treatment, lol!

End of Dwelling......:hide: !

BeelzeBob
05-03-04, 12:55 PM
OK, I'll be the Devil's Advocate...
Dwelling........

1) What proof do you have it's the additive and not an inferior winding insulation? GM, like other manufacturers, make mistakes. It's called a recall.
2) Try the search on an additive based Forum for different results. Some additives are recommended. (Mopar and it's CCC for Carbon cleaning for example. Auto-rx by many)
3) Any valid statistics on Fuel pump failure on additive users vs non-users?
4) Any valid statistics on cost of Pre-ignition damage vs Fuel pump replacement every 100,000 miles.
5) Any valid statistics on how many oz's of additive it takes to destroy a fuel pump, if it does?

Not bad, for a guy that doesn't use it in his N*, huh!
I'm going to try the Auto-rx treatment on my Toyota 4x4 w/360k to salvage the seals that are beginning to emit the puff of smoke at start up. It will be my first serious use of an additive.

I did like the bit about adding a can of additive and then going to the pump.
Maybe it's shock treatment, lol!

End of Dwelling......:hide: !


Valid statistics...???? With a lead in like that no matter what I say you will question it....!!!!....LOL

I have seen the various GM electric fuel pumps run on a variety of test fuels, gasoline, alcohols, MTBE, sour fuels (heavy peroxide content), etc.... for thousands and thousands of hours in fuel test rigs, running engines, dyno cells, etc. Rarely if ever is there a failure and I have personally NEVER seen the insulation on the armature short out due to solvent attack or damage.

BUT....I have, as stated, seen hundreds of pumps returned from the field that are in perfectly fine condition...except that the insulation is destroyed on the armature windings due to solvent attack. Since the pumps ran for quite awhile before they failed I would think that the insulation material was originally OK and lived for quite awhile in gasoline until some solvent came along that attacked it.

Just "circumstantial" evidence I know but....without creating a research project or divulging proprietary info that is all you get....LOL.

There are some recommended additives for cleaning the injectors of deposits that are endorsed by the manufacturers. I would have no problem with those if they are used as prescribed. The problem is that once someone perceives that the OEM recommends "their" additive they assume that "all" additives are OK...not the case. The additives that will clean and not attack the fuel pumps and injectors are often much more expensive...so the cheaper aftermarket additives are used instead...with poor results. OR, as described the additive is put into the tank full strength and the car run without diluting the additive correctly, damageing the pump.

Just a few ounces of solvent will destroy a pump if it is not diluted.....That is why putting the solvent/additive in the empty tank full strength and then driving to the gas station takes out the pump so fast. It is not the "shock" of the solvent but the fact that the solvent is undiluted and that the pump is pumping it and recirculating it thru the fuel system constantly until the tank is filled. Not hard to understand that putting the stuff in an empty tank and then running the engine/fuel pump before diluting could cause damage.


BTW...GM makes some of their fuel pumps over the years, but, by and large, the fuel pumps come from a variety of sources such as Bosch, Nippondenso, Hitachi, Walbro, etc.... All of those pumps I have seen damaged by solvent attack...so...it is not just the wire insulation that "GM" uses that is "inferior" if that were the problem.

My own personal experience and experiment (inadvertant that it was....LOL) involves my parts cleaning tank at home in my garage. It is an old 55 Gallon oil drum cut in half on it's side (a la ghetto barbecue) on legs with dual/dual filters and a Bosch external mount fuel pump to circulate the fluid. The fluid is mineral spirits and the cleaning fluid is filtered before and after the pump by separate dual filters. This home-made setup has been with me for over 25 years and is used constantly by me and every person that works on anything in my garage. The pumps live FOREVER......unless....some idiot uses Gumout carb cleaner any other carb cleaner or spray and puts it in the cleaning tank or uses the tank as a catch basin for spraying out a carb. It takes the pump out everytime. Gumout, in specific, has destroyed several Bosch pumps, the same pump made by Diesel Kiki in Japan (I would assume this is a completely different source for the armature winding insulation....) and pumps made by GM and Walbro. BTW....there is a large red sign over the cleaning tank that says "Put NOTHING but dirty parts in here"....LOL

So....I do not need any further proof or statistics that carb solvents or fuel system cleaners can damage fuel pumps. Some might not but I am not going to do the research on MY equipement to find out.


Not sure of the connection with the "preignition" question or what you are fishing for there....??? Care to clearify?

OlManRivah
05-04-04, 12:17 AM
Well....I used Pre-ignition as an example of a situation where a person might use an additive to prevent or cure a problem (Pinging) without the need of hauling their car to a Dealer. Possibly, to avoid the de-carboning procedure at the Dealer, as an in that example. This additve may also delay other problems, like carbon on fuel injectors, water in gas, or other conditions.

Weigh this against the occassional fuel pump replacement every 100,000+ miles or so (assuming the addditive is causing fuel pump deterioration).

IF (notice I say IF), the additives work, it might be cost effective to put a pump in once in awhile, instead of the cost of dealing with the other problems, which if done by the Dealer, could become quite costly.

This may have been a bad example, but, I guess you get my drift....:drinker

Koz
05-04-04, 02:04 AM
Hey I see every one is pointing at the fuel pump.

How old is the fuel filter it might be clogging and will cause the same problem change it its about fifteen dollars.

everyone on here always takes the hard and most expensive route first.

BeelzeBob
05-04-04, 11:58 PM
Hey I see every one is pointing at the fuel pump.

How old is the fuel filter it might be clogging and will cause the same problem change it its about fifteen dollars.

everyone on here always takes the hard and most expensive route first.


Could be....good point.....but if it was a fuel filter you would expect the restriction to be worse when the flow thru the system is higher...higher demand. The reported symptoms with the fuel pressure gauge indicate that the pressure is low even at idle when the demand is almost zero...It might be the filter plugged...but if it were THAT plugged the engine wouldn't even run at all I would expect. Still, a good thing to check before dropping the tank.

macx
05-05-04, 12:11 AM
That makes good sense, but I had changed
the filter only 3 weeks ago.

When I found low fuel pressure irregardless
of rpm (20 to 25, sometimes under 20 at
idle even) and being I had already changed
the regulator and relay, I went for the pump
as it was the only directly pressure-related item left.

After changing it (see my later post - it went
unexpectedly well and easy!), I hooked my
gauge up and held the bleed button while
my wife turned the key on (not starting the
engine) to purge the air.

As soon as the air was out, I released the bleed
button and immediately had nearly 50 lbs pressure!

The engine started immediately (not like before
with having to crank it for 10 seconds or more to
get it to start) and ran at 40 lbs, both at idle
and when revving it up sharply, and at 50 with
the vacuum off the regulator.

Now it runs like it used to with instant throttle
response and very good power.

Case solved!

I figured out partly why the pump assembly
is so blasted expensive - instead of just the
pump itself, everyone sells the complete
assembly including gauge sender, housing,
sump or well, all the wiring, and even the
part the external lines hook to.

Out of curiosity, I tried taking the pump out
of the assembly and it was very simple.
I'm sure that would lower the price somewhat
from the roughly $250 aftermarket cost
for the whole assembly!

Logandiagnostic
05-05-04, 04:12 AM
The pumps are available. I think you bought a whats called a 'hanger unit.' Basically a drop in complete fuel pump assembly. Those go for about $3-350.

The pump itself is about a $90 part.

Logan
www.airbagcrash.com
www.logandiagnostic.com

BeelzeBob
05-05-04, 12:50 PM
You might look at the old assembly that you took out and carefully inspect the wiring to the pump...it is probably melted or damaged by heat. Very common when a fuel pump fails....one reason that the entire assembly is serviced....

FlashRed
05-06-04, 01:46 PM
You might look at the old assembly that you took out and carefully inspect the wiring to the pump...it is probably melted or damaged by heat. Very common when a fuel pump fails....one reason that the entire assembly is serviced....
if the wiring is Not melted or damaged but the mileage is over 100k should the entire assembly be serviced.

macx
05-08-04, 10:50 PM
Yeah, probably just as well.

I looked closely at the wires,
undid the plugs, everything
looked fine. BUT it did have
about 120k on it.

I have used injector cleaner
very sparingly, and only
when filling it up at the time
of fueling.

Does anyone know what
brand is recommended or for
sure will NOT cause damage?

Thanks!