Seville Fuel Pumps


Old 12-26-02, 08:53 AM
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Seville Fuel Pumps

This EPIC is my complete question as I submitted it to the Cadillac Customer Assistance Center. They returned a generic "We don't have such technical data" recitation. Their site started with VIN and other carographic data. If ya'll can help I will focus on extravagant reincarnations for at least one of you (you choose who).

I am seeking technical reference data on components in the fuel system of a 1976 Seville. Do you have a technical library staffed by a reference person that would have detailed information going back to that year?
LET ME START FROM THE BEGINNING. I recently purchased a 1976 Seville for the impulsive reason that it reminded me of a Seville my father used to drive me around in. I quickly discovered that the car had been “jury-rigged” to keep running without correct dealer servicing and probably without the correct replacement of some important components, primarily the Electronic Control Module (ECM).
After a week of care-free riding the engine sputtered off immediately after a start-up and I determined that the engine was not getting petrol. The sound of the electric Fuel Pumps, which had been audible from the driver’s seat (first red flag??) when I test drove the car, was absent. I pulled and drained the Fuel Tank, removed the In-Tank Fuel Pump (ITFP) and the Chassis-Mounted Fuel Pump (CMFP) along with the Chassis-Mounted Canister Filter (CMCF) and inspected all tubing. Upon testing both Fuel Pumps with very low current I found they had visibly brisk flow, but I had no technical electrical or flow specs or flow measuring equipment.
When I inspected the wiring --- tracing it back toward the engine compartment --- I discovered that the wire had been replaced and that it was spliced into a 14- or 16-guage red shielded lead clip-locked onto the relay side of the Distributor Cap. It also had an in-line 30 amp blade type fuse (propped up approximately in front of the Master Cylinder) which was blown. I reinstalled the Fuel Pumps and Canister Filter after replacing the Sock Filter on the ITFP and the Filter Cartridge in the CMCF.
With the Fuel Tank back in place and refilled, the blown fuse replaced, and my amateur fingers crossed, I turned the key, STARTED THE CAR (!!) and drove it immediately to my local Cadillac dealer for a thorough inspection of my work and of the entire car. (I also asked Brasington Service Techs to try to identify the relay or sensor I had found lying loose near the AC compressor; it is marked “G551258 / A(?)1764433F(?) / THERMAL / 169C” with a tab for bolting on the firewall or wherever and three spade terminals labeled ‘S’, ‘B’ & ‘C’. The plug clip-locked to it has three leads: A – a black 12” wire with a press-on terminal cap, B – clipped black wire, and C – clipped green wire.) The service manager told me about the ECM and other seat-of-the-pants rewiring --- which I already had an inkling of --- and told me they could not stand behind any work on the car. This in a phone call in which they also told me the engine had died on them and they couldn’t get it started and could I come get it! I retorted that I had gotten it started and I’m no mechanic; further it seemed backwards to drive it in to service and tow it out.
They tried some more, charged me around $100 for supposedly re-routing the power supply wire to the Fuel Pumps and I drove the Seville out for about 10 miles of use before it quit again for lack of petrol. This time the in-line fuse in the power line to the Fuel Pumps (the same wire that was there before the dealer service as far as I could see) was blowing repeatedly. I replaced the fuse NINE TIMES last Friday evening during the last half of the 1.1 mile drive to my duty shift at Shands Hospital. Yet this sedan will run indefinitely sitting still in Park --- or even in gear with my foot on the brake. But as soon as I start moving it achieves VARIABLE distances before the in-line fuse to the Fuel Pumps blows again
This car is looking like a tougher case than any of the transplant patients I’ve worked with, but I don’t want to give up on it for sentimental reasons, as stated above, and because it has only 96K original miles. If the upholstery, finish and vinyl top weren’t so weathered I might even consider having the dealer do some rewiring and replace the whole fuel system but I shall continue trying my own hand for the present.
My guesses at the current problem are:
(16) Damage in the electronics of one or both Fuel Pumps is creating an intermittent ground fault; and/or
(17) The replacement wire has some break-down in the insulation somewhere and is in contact with ground --- perhaps somewhere that heats up during operation and increases the contact (but why would it EVER start if this is happening?); and/or
(18) The 30-Amp fuse is too small (but I don’t dare go higher without knowing how much current the Fuel Pumps can handle); and/or
(19) The Fuel Pumps are exerting a variable current draw that tops 30 amps as the engine heats up and accepts swifter petrol flow; and/or
(20) The power source out of the distributor to which the Fuel Pumps are spliced is variable or intermittent-with-spikes and it’s frying the fuse.

I considered plugging in larger fuses, but 30-Amp is the maximum in blade fuses where I shop and that might damage the Fuel Pumps anyway … also considered plugging in a blade-type 30 Amp circuit-breaker, but was unsure whether to try the cycling or non-cycling type. Maybe I should REALLY replace the power supply wire to the Fuel Pumps making sure it’s thoroughly shielded in plastic conduit all the way. Or maybe I should connect that wire into another power source like the fuse block. So my main questions are:
(M) How many amps of current can the Fuel Pumps tolerate?
(N) Does the described lead from the Distributor give a varying or intermittent current?
(O) Can you identify the function/location for the mystery THERMAL relay?
(P) COMPLETELY UNRELATED QUESTION – What kind of bonding agent (susceptible to what solvent) held vinyl tops in place in that model year?

Can somebody there help me avoid calling Click ‘N’ Clack on National Public Radio and probably being humiliated on the air ?? PLEASE ??
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Old 12-26-02, 04:51 PM
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A couple of things:

1) If you plan on keeping this car, the first thing you need to do is to buy the GM service manual for it. It will pay for itself ten times over, even if you have to supply it to the mechanic doing the work. You can find them new from or used on the web through the various book vendors that go to swap meets and tour the country and sell through the web. Dan Bower is one guy that should have your book(s)[email protected] is his e-mail. By far, the GM book will show you more than any other manual out there.

2) It has been jurry rigged. The dealership is 100% right, they cannot guarantee what they do or their work as it was not of their doing. They also cannot guarantee if it will ever work right because a lot of hands have been in it. You can't expect them to rework miracles on a butcher job without a hefty bill on their part.

3) These early Sevilles are big money pits. Get used to spending money like water, and frequently. The Bendix fuel system was in early stages and use in 1976 and was very troublesome. The solder joints on the electronic controllers failed. The electronics and sensors go bad and are quite costly. Also, this is the first year for this Seville, and the bugs weren't worked out. You will put thousands into this car, and if you scout Hemmings, you can buy a MINT one for probably less and enjoy it more and service it less! Look at

4) Sounds like a viscious short. I would skip the Caddy dealers---too old for them to want to bother with it and most of the techs working there are probably not used to those old time systems. Find a ASE certified shop in your area that will spend the time to figure it all out. Don't squawk about the price too much---they have every right to charge you what it takes to get it right, after all, they didn't do the butchering job. It may take them a long time to redo this previous "repair".

5) My personal opinion? Pitch this thing now while you're ahead. If you are hell bent in buying a 1st generation Seville (76-79), you can find a MINT one for probably less than you'd spend to fix this one. Use this one for parts on the better one. You'd be cheaper in the long run and even if you got a Seville that needed work, chances are it wouldn't be butchered like this one. You have wiped paint, a bad vinyl top, and other maladies. Unless this PARTICULAR car means something to you, you're best off to pitch it. It's a bad, bad money pit.

6) The Seville uses an intank and a external pump to my knowledge. Make sure it's your problem before spending the money on them---again, quite expensive. I'd bet the poor wiring job is the cause of all this.

7) Were any of these problems inherent in your inspection and test drive of this car? Did the owner hide anything that you directly asked? If so, you MAY have recourse if the person lied to you---depending on the proof you have and the state. Most people sell you a car "AS IS" and write that on the bill of sale. I do, but I let the person bring an expert and answer any questions they ask.

8) The Caddy hotline if anything, will refer to you a club, organization or source for information as GM doesn't keep information on models over 10 years old. Parts also tend to dwindle when it gets old--unless it's very popular (such as the Vette, Firebird, Camaro, Chevelle, GTO, etc).

9) The 76-79 Seville actually rides on a Chevy Nova subframe and shares many of the same front end parts as my Trans Am. LOL. About the only GOOD thing about these is that they are rear wheel drive. Not bad looking cars, just severe, severe, money pits.

10) Parts will be hard to come by such as wiring harnesses and such. They will either have to be fabricated by hand to OEM spec ($$$$, although there are companies that do it) or a used Seville harness found and grafted into this car. That's quite labor intensive and you're STILL dealing with 27 year old wiring!!!

I've given you ten reasons to think about this one---but the decision's up to you.
Old 12-27-02, 03:33 AM
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I believe the relay may actually be a thermal fuse for the A/C compressor. Does it look like this?

If your serious about fixing/restoring this than get a subscription to Hemmings Motor News You will be able to find any part for your Caddy there. You might also want to pick up your own Factory Parts Manual so you dont have to "bother" the dealer. I did this for my 72 Pontiac, and my other 3 vehicles.

Do your self a favor and pick up the following least the Shop Manual and the Fisher Body Manual from
Need more help let me know. you'll have to trace that fuel pump wiring to find any shorts and will need the Factory manuals.

1976 Fisher Body Service Manual (Seville)
Price: $20.00 In Stock

1976 Seville Owner Manual
Price: $20.00 In Stock

1976 Seville Shop Manual
Price: $60.00 In Stock
Old 12-27-02, 04:37 AM
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I agree with Stevo, except for one thing:

Helm doesn't supply parts manuals. TUAR-Grimbac does. They may have obsoleted the printed parts books. In this case you need the 76-81 Cadillac parts book and illustration book. I believe it is catalog #60 and 60A or 61 and 61A, can't remember which off the top of my head.

If TUAR-Grimbac has obsoleted the books, then either you have to find them used on Ebay or the net, or, buy them in microfiche format from Bell & Howell in Wooster, Ohio. You'll need a microfiche reader to use it, or most public libraries and universities have ones you can use.

Old 12-28-02, 12:06 AM
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I can help you find a parts book, thats the easy part of restoration.
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