Secondary fuel pump and chip problem

[vanvan2801]

Hello everybody !

I am from Belgium and I own a ZR-1 Corvette from 1991 for a few weeks. I am not familiar with the history of the car.
I noticed two things:
1) that when I was in FULL mode, above 4000 RPM, nothing more happens. Knowing that the secondary fuel pump activates at around 4000rpm, I decided to check if it was working by removing the fuse from pump 1, so I tried to start the car (cold) but nothing happened. Then I checked to see if the pump wire was plugged into the ecm..it was. So I assumed that pump 2 was out of order. So I ordered 2 new pumps (you might as well change both) after replacement, I repeated the test by removing the fuse and unfortunately, it did not start .... then a road test ... the same thing , it does not exceed 4000 rpm ... I have from time to time the code 41 which appears ....
What do you think? Perhaps the secondary pump relay causing the problem?

2) it is also important that I tell you that part of the vacuum system has been delete (electric vacuum pump, secondary port vacuum tank,...) so I assume that the secondary actuator system is in the open position..so logically a special chip should be installed ..but after checking i still have the original chip (DELCO AXFK 0277). so the full mode cannot work if a special chip is not present ?? - have you ever faced this problem?
Here is some picture of the current chip..
I hope you understand. my english is not very good..
Thank you in advance !

[Young1]

Research on this site on how to check your fuel pressure then report back.

[Ccmano]

You replaced the fuel pumps so that is likely not the issue. The chip concerns me. With the secondary delete you should have a specially coded chip that makes operation in that mode possible. It looks like you have the wrong chip. That, to my knowledge, is not even an LT5 chip. The standard chip should really be a BFXBG. I would not run the car that way. Damage due to a lean condition can result and is likely why it won't go over 4000rpm. Code 41 is a memcal (chip) error, so likely related. Get the right chip in there and start from there. I would call Mark Haibeck and purchase a correct chip. Www.ZR1Specialist.com. But don't drive the car till this is resolved.


The more I look at your photo of the chip, it looks like someone has modified it in some way and not in a good way. As I said, call Mark Haibeck,
H

[vanvan2801]

Thank you very much for your response, I send an email to Marc right now.On the other hand i didn't think of saying that the engine is from 1990 ... so i don't know if that changes anything? so you think the pump problem is related to a bad chip? even if the test with the fuse doesn?t work?

[ram_g]

Vanvan, I am by no means an expert as I am just learning about my own ZR-1 that I recently acquired. However there are a couple of things I'd like to point out.
- I am not sure why you are assuming that the secondary air intake flaps are in the open position just because the vacuum system was deleted. Did someone confirm to you that they wired open the secondaries or fully deleted the hardware? Seems to me that you need to check this somehow - probably by pulling the plenum (get Marc Haibeck's explanatory DVD before you do this). If your secondary air intakes are not opening via vacuum as they were designed, or wired in the open position, then it doesn't matter what the secondary pump does.
- There is a way to check if both pumps are working by checking the amps (NOT volts) when you ground the fuel pump test wire (single wire and connector near the ECU). If both pumps are working you should observe 8-10 amps, if memory serves. If you have half of this, only one pump is working.
- I agree with the observation that the chip looks a bit odd.

[vanvan2801]

thanks for your reply ram g. as you say the best solution is to disassemble the plenium in order to see more clearly what has been done. but I was wondering if there was a way to see this, without taking everything apart? but at first glance the secondary system is delete because, they deleted the electric vacuum pump, the secondary tank I think (see photo I took when changing the alternator and I circled a delete vacuum pipe)
anyway thank you for your answers, i appreciate it very much.!

[Paul Workman]

Perhaps you already have discovered this, but for other new owners, maybe this info will be useful. So, I apologize if this is redundant for you!

You can easily check the fuel pumps current draw via the diagnostic (testing) connector protruding from the (large) wire loom near the windshield wiper motor (see photo of the red wire and connector)

By configuring a VOM to read amperes, you can connect the VOM in series between that test connector and the POSITIVE battery terminal.

Each pump draws between 4-5 amperes each for a total of 8-10 if both are working properly.

This diagnostic test is conducted with the ignition switch in the OFF position

NOTE: As you have indicated, to determine which pump is or is not working up to expectations, by pulling the fuel pump fuse (located on the side fuse panel - accessible by opening the passenger side door) by elimination and observing the amperage draw you can determine individual performance.

For a dynamic test, taping a fuel pressure gauge to the windshield and going for a drive will confirm whether or not fuel delivery is an issue. My 1990 fuel pressure when cruising in normal mode is 44-45 PSI (~45 PSI or 310 KPa) and at Wide Open Throttle (WOT) pressure jumps to 55 PSI (~379 KPa).

One other thing that gets overlooked is the accordion bridge hose between the air filter box and the plenum intake horn. As they age, they sometimes will collapse at full throttle, thus pinching off the air flow...AND it occurs beginning right about 4000 rpm! It is an easy fix tho.

• Marc supplies some wire loops that fit inside of that hose to keep it from collapsing.
• Or, (as I did) you can construct a sleeve and insert it inside of the hose. (I used aluminum sheet metal and pop-rivets to fabricate mine. Inexpensive, invisible from the outside, and works great!)
• OR, you can install one of the smooth custom hoses (from Jerry's Gaskets) which work nicely and look very nice.

Removal of the vacuum pump suggests the secondaries are eliminated either entirely including the actuators and associated plumbing and the throttle plates (SPTs), OR as some do - just zip-tie the SPTs open and leave the plumbing in case one wants to revert back to stock later. And, that said, if the secondaries are removed or tied open, then the FULL ENGINE POWER indicator on the dash should be illuminated and the manual switch should be permanently in the FULL position (1990s only. 1991+ have a momentary toggle switch (key) that illuminates a green light when in FULL POWER mode - and must ALWAYS be illuminated if the secondaries have been deleted [mod])

[Ccmano]

Originally Posted by vanvan2801

Thank you very much for your response, I send an email to Marc right now.On the other hand i didn't think of saying that the engine is from 1990 ... so i don't know if that changes anything? so you think the pump problem is related to a bad chip? even if the test with the fuse doesn?t work?

The chip you showed a photo of does not go to any year LT5 engine based on the numbered sticker. It is missing it's blue cover and the smaller chip you see on the top of it appears to have been added. I don't think you have a pump problem at all. The chip commands the fuel pump relay. If the chip is bad there is no power from the relay to the fuse. In any case take this one step at a time.
H

[Perry Mitchell]

[QUOTE=Ccmano;313037]The chip you showed a photo of does not go to any year LT5 engine based on the numbered sticker. It is missing it's blue cover and the smaller chip you see on the top of it appears to have been added. I don't think you have a pump problem at all. The chip commands the fuel pump relay. If the chip is bad there is no power from the relay to the fuse. In any case take this one step at a time.
H
[/QUOTE

The Delco AXFK 0277 is the correct original chip for a 91 Z, although it is missing the blue cover and appears to have a piggy backed chip installed.

[Ccmano]

[QUOTE=Perry Mitchell;313046]

Originally Posted by Ccmano

The chip you showed a photo of does not go to any year LT5 engine based on the numbered sticker. It is missing it's blue cover and the smaller chip you see on the top of it appears to have been added. I don't think you have a pump problem at all. The chip commands the fuel pump relay. If the chip is bad there is no power from the relay to the fuse. In any case take this one step at a time.
H
[/QUOTE

The Delco AXFK 0277 is the correct original chip for a 91 Z, although it is missing the blue cover and appears to have a piggy backed chip installed.

I stand corrected, I was looking at the code for the updated chip BFXB by GM for 91. The OP States the engine is actually a 90'. This could be part of the problem. Nevertheless his code 41 will prevent any sort of secondary operation above 4000 rpm. I'm still inclined to think the chip is the primary problem here. Especially one that has been modified like this.
H