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HI everyone, Well I get to test the theory that states, "There are no stupid questions, only stupid answers!" My first Vette ('88 C4), First repair, luckily, a VERY easy first repair!
All signs point to the fuel filter, which has probably never been changed, I am well aware that the very low fuel pressure that I'm reading (15-20 psi) will probably be a faulty 'fuel pump, regulator, in tank strainer, or even the relay. I have even experienced what looked like a cats hair ball, plugging a line, the long one from the tank to the fuel pump ('57 Belair, stock 283 mechanical pump at engine front) I used a shop rag wrapped around an air line, then pressurized the tank at the filler (behind the left fin, for those who don't remember, or didn't know). Out it popped!
But, the filter first! Only problem is, I can't find it!!!! This is the stupid question part, I feel stupid that I cannot find the filter! Yep, even with the kinda good excuse that Chilton told me "In the rear of the vehicle". Mounted to the frame rail, with photos! Too close to locate. Where is this in relation to the outside of the vehicle?
Cannot seem to find it! I suspect it is on the other side of the frame rail nearer to the blower motor, NOT the rear of the vehicle. The photo's are all 'too close' to determine the location. Is it only visible from the underside? Before the line goes to vertical from horizontal, near the engine. Moving back, how far? WHERE is it ?? From outside is it even with the front door gap, door handle, the center of the rear glass?? A kind word from any of you who has changed one before would brighten my whole day!
And while I have this open, is there a quick answer to the question of the pump? Is stock the best bet? Or, is a larger higher pressure, higher flow pump good for performance, as the ads state? I'm thinking about a Kemso 340LPH (***) that is rated for 340 lph, @ 43-90 psi. (Which I can adjust to 45 psi, or whatever runs best) a performance increase would be great! But reliability is the primary reason for this choice. I have never had, nor seen one go bad (yet!) Used several on a variety of vehicles, with 100% success rate so far! First one was installed over 15 years now on a Subaru that is still driving daily. Very reliable electric pumps!
Thanks in advance !!!!!!
R.P. (C4VetteAddict)
I have an '88 C4 coupe and my fuel filter is under the passengers feet. On your pump be sure to check everything before replacing it. There are many things that can cause low voltage issues to appear in a C4, be careful throwing parts here as it can get really expensive. Do you have a Factory Service manual for the 1988 year Corvette? It has some very good trouble shooting charts in it regarding the fuel system.
There was a lot of corrosion on the battery positive post behind the battery mounted on the frame rail in back of the battery. After cleaning ALL the connectors the voltage drop I had seen inside the car was much improved. After cleaning the ground wires and straps I had full battery voltage everywhere in the car. This particular post has several fusible links getting their power from it, it is critical to clean this because if you have any corrosion at all as it affects a good deal of the accessories and other items on the inside of the Corvette.
Try to get a voltage reading of the wires feeding the fuel pump. I tested mine at the Fuel pump relay and at the fuel pumps's wiring harness,. If you don't have a solid 12 Vdc and a good ground to your pump, it will not run as well as it could providing it with full voltage. The harness attaches to the fuel pump under the gas cap area. It is not to hard to access just be careful as you might have fumes there. On my car there were three wires, one for the fuel pump +, one for the fuel pump Ground and the last is for the fuel gauge. The big wire is 12+, the middle wire was ground, and the last one for your fuel gauge. Be sure the ground here is good, clean all the connectors as you go. I use a tool called a POWER PROBE 4 for testing my cars electrical systems, it allows you to supply either Positive or Ground at the tip based on what you want. When I plugged it in directly the pump the motor started immediately. Just be careful how you do it as you really don't want too many sparks over the fuel tank....
If you have 12 volts plus at the fuel pump when running then it should produce the needed fuel pressures for the car to run. If the pressure is still reading low after the fuel filter change then you might need a new pump. Check your Fuel Pump relay (mounted on the firewall) and be sure it is not part of the problem. Test it carefully or swap it for a known good relay. The 1988 Corvette uses this same relay in multiple places so I keep a new spare in my glove box.
I ended up replacing my fuel pump after doing all the tests, only to find out that my fuel supply line was partially blocked and that required a new fuel line. People with lifts can easily damage brake lines and fuel lines. On the 1988 C4 it is easy, left side will crush brake lines and right side will crush your fuel supply and return lines. Be careful when raising your C4.
If you do change your pump be sure to get a piece of Fuel Injection Hose and the necessary clamps designed for being submersed in gasoline so you can eliminate the little gadget that mounts on the fuel pump lines to stop or slow the pulsing effect of an electric Fuel pump. It is very easy to change out when you do it but I would strongly suggest you put some penetrating oil on the bolts that secure the fuel pump assembly into your fuel tank. A little Kroil Oil works wonders and makes the parts come apart easily.
There are several ground straps on these cars as well, they are very important if you want everything to operate. I had one that had come off the exhaust and after reconnecting it the power antenna started to work again.
Please tell us here at the Forum what you found to be causing the problems you were experiencing as it helps us all learn more about out Corvettes!
I have an '88 C4 coupe and my fuel filter is under the passengers feet. On your pump be sure to check everything before replacing it. There are many things that can cause low voltage issues to appear in a C4, be careful throwing parts here as it can get really expensive. Do you have a Factory Service manual for the 1988 year Corvette? It has some very good trouble shooting charts in it regarding the fuel system.
There was a lot of corrosion on the battery positive post behind the battery mounted on the frame rail in back of the battery. After cleaning ALL the connectors the voltage drop I had seen inside the car was much improved. After cleaning the ground wires and straps I had full battery voltage everywhere in the car. This particular post has several fusible links getting their power from it, it is critical to clean this because if you have any corrosion at all as it affects a good deal of the accessories and other items on the inside of the Corvette.
Try to get a voltage reading of the wires feeding the fuel pump. I tested mine at the Fuel pump relay and at the fuel pumps's wiring harness,. If you don't have a solid 12 Vdc and a good ground to your pump, it will not run as well as it could providing it with full voltage. The harness attaches to the fuel pump under the gas cap area. It is not to hard to access just be careful as you might have fumes there. On my car there were three wires, one for the fuel pump +, one for the fuel pump Ground and the last is for the fuel gauge. The big wire is 12+, the middle wire was ground, and the last one for your fuel gauge. Be sure the ground here is good, clean all the connectors as you go. I use a tool called a POWER PROBE 4 for testing my cars electrical systems, it allows you to supply either Positive or Ground at the tip based on what you want. When I plugged it in directly the pump the motor started immediately. Just be careful how you do it as you really don't want too many sparks over the fuel tank....
If you have 12 volts plus at the fuel pump when running then it should produce the needed fuel pressures for the car to run. If the pressure is still reading low after the fuel filter change then you might need a new pump. Check your Fuel Pump relay (mounted on the firewall) and be sure it is not part of the problem. Test it carefully or swap it for a known good relay. The 1988 Corvette uses this same relay in multiple places so I keep a new spare in my glove box.
I ended up replacing my fuel pump after doing all the tests, only to find out that my fuel supply line was partially blocked and that required a new fuel line. People with lifts can easily damage brake lines and fuel lines. On the 1988 C4 it is easy, left side will crush brake lines and right side will crush your fuel supply and return lines. Be careful when raising your C4.
If you do change your pump be sure to get a piece of Fuel Injection Hose and the necessary clamps designed for being submersed in gasoline so you can eliminate the little gadget that mounts on the fuel pump lines to stop or slow the pulsing effect of an electric Fuel pump. It is very easy to change out when you do it but I would strongly suggest you put some penetrating oil on the bolts that secure the fuel pump assembly into your fuel tank. A little Kroil Oil works wonders and makes the parts come apart easily.
There are several ground straps on these cars as well, they are very important if you want everything to operate. I had one that had come off the exhaust and after reconnecting it the power antenna started to work again.
Please tell us here at the Forum what you found to be causing the problems you were experiencing as it helps us all learn more about out Corvettes!
Best regards!
Thanks for the good advise! I haven't had to change the pump yet, changing the filter did the trick! So far, I have completed the intake mods (cutting a larger hole in the front of the air filter case, removing the screens on the MAF, bypassing the coolant to the throttle body. I have also repaired the cruise control by adjusting the clutch and brake switches, repaired the dark spots on the display by replacing the burned out bulbs (and ordered a complete LED for the interior set form Amazon for about $25.00), Made the tool for a stuck hood, and replaced the broken clip that holds the cable on the release mechanism. Replaced the plugs and changed the oil, installed a new stereo. I followed links in this forum for most of the information, including the excellent link concerning oil! Now the AC is the only thing still in need of repair. I had forgotten that Vette's are loaded! More standard features than a Cadillac I once owned!
I LOVE this car!! It is fun, comfortable, quick, handles like it's on rails! I keep finding reasons to drive..... Anywhere! My one regret is that I did not buy one years ago!
No stupid questions?
