I just finished a TBI to TPI swap and can't kep the thing running. The swap is complete and done right. There's nothing I didn't change over but I'm not holding fuel presure. My pressure goes up to about 14 psi then quickly dies down a few seconds later. I tried an adjustable fuel pressure regulator but it made things worse. If anybody has any ideas please let me know as soon as possible. This car is my daily driver and I'm not able to get to work or anywhere else till it's done. Thanks.

 

Did you also change the factory pump to match the TPI? The normal pump will put out about 40 psi with just the key on.

 

I have a Granatelli fuel pump. Brand new. I also got the TPI fuel lines. Like I said thee's nothing I didn't change. This is what really confuses me.

 

Well, step one is to verify that the pump is able to put out the proper output... I'd start by pinching off the return line to the tank and pressurizing the system... See if that gets you decent pressure.. If it does, your regulator is shot. If not, then you need to verify that your injectors aren't leaking or anything (probably not).. If all that checks out, I'd put another fuel pump in...

 

I'm sorry, let me get more specific. The fuel pump is a brand new granatelli that puts out 255 lph. I just replaced the fuel pressure regulator and I'm still having the same problem. I get about 15 psi when i first turn the key and the pump primes but it quickly dies down to nothing. There are no external leaks, the wiring is all good, the fuel lines are new, and the injectors aren't leaking anywhere externally. Could I have an injector or maybe a few of them stuck open and what would cause this?

 

Well, you basically know that it is fuel related so here is what I would do.

Check voltage at fuel pump, I dont care if your wiring is okay or not, check the actual voltage to the pump and the fuel pump grd.

Prime the car and block off the return line like was mentioned and see if you have any change.

Then prime it again and block off the feed and return lines. If the ressure still drops you have some issue with the injector or the AFPR is leaking. Which means you will be pulling the rail up and taking a look.

Long story short, u either dont have the prssure in the first place from the pump(its bad) or u have a massive fuel leak, whether it be at regulator or injector..

Adjustable regulator with a screw backed the entire way out?

Or no metal plate on top of afpr (internally to adjust)

Throwing out any ideas I have since I'm not there

later
Jeremy

 

Thanks for all of the ideas but unfortunately I've already checked all of that. I put my stock fpr back on and replaced the internals so that's all good. I also blocked off the lines and checked voltage at the pump. I checked the injector harnesses and every one was working perfectly fine so I don't see the fuel going anywhere but through the injectors. They have to be stuck open since there's nothing left to check. I just really want to know what could have fried them. Once again thatnks for all the help and if anyone has any other ideas please let me know.

 

If the injectors are the problem and this much fuel is leaking into the cylinders, all your plugs should be wet, very wet.

My experience has been that the standard pump will put out a lot of volume at the standard pressure. If your fuel pressure is dropping to 15psi and then almost zero, I would think your cylinders would have a great deal of fuel in them. You might try taking out all of the plugs and cranking the engine over for ten or fifteen seconds and see if fuel is being discharged from the spark plug holes. Just don't have any source of spark near by.

 

This happened before. My plugs were completely soaked. The odd thing is I had the car running a few weeks ago at the garage while it was hooked up to a fuel system cleaning machine. I guess with the machine's pump being adjustable it got the psi that it needed but it wouldn't start as soon as I ran it off the car's fuel pump again. Like I said everything else checks out completely fine except for the injectors. When i tested the injector harnesses they were pulsing fine during cranking but when I checked the injectors themselves there was no pulse at all. I also noticed that the injectors had way too high of an ohm rating. Stock is between 11 and 14 ohms while mine were all over 16. I thank everyone for any info and if anyone knows anything else about this please let me know.

 

You've probably got a pinched fuel supply line, or clogged post filter, or clogged tank filter. OR...
Did you install the pump "in-line" or "in-tank." If you did inline, did you remove the previous in-tank one, or are you powering them both? If your trying to suck through an a pump that's turned off, well, there you go.

New parts aren't always good parts either.

 

I agree with redngold, just because it is a brand new in the box fuel pump doesnt mean anything. I have had brand new junk before myself. There are only so many things it could be. Happy Hunting.

 

Stupid question but, did you install the fuel filter backwards?

I've seen that cause low fuel pressure before.

 

I agree about new parts not always being good parts but everything was tested and it's all fine. Nothing's installed wrong or pinched off. The fuel filter is in the right way and the fuel pump is an in tank which tested fine. My spark plugs are soaked in gas and there really aren't any other options. Thanks for all the help and I'll post any progress on here by tomorrow night.

 

Perhaps I'm going to sound like an idiot here, but taking your post at face value, you state that pressure "goes up to about 14 psi" then drops to 0. I've never tested fuel pressure, but I assume you let the system prime and watch it?

As I read it, you installed a low pressure pump that simply doesn't generate the 43PSI (or whatever) that TPI uses. 14PSI is TBI or regulated carb pressure.

Again, maybe I'm missing something, but your post states it goes up to 14psi. It needs to go much higher for TPI. (probably wouldn't explain the bleed off, but not enough pressure off the bat)

 

The 255lph pump is fine, provided you have the voltage to drive it.
The short primer time doesn't help when trying to set the static (engine of, or WOT) pressure.
My car won't start with less than 30psi.
There is a fuel pump diagnostic terminal on the ALDL connector. Termianl "G", lower left pin, apply 12volt (with the key off) to power the pump continuously. I have the same type of pump and with the AFPR I set it to 43psi. if you dead head the pump with a gauge attached, and the pressure doesn't hold then it's the pump's check valve that is faulty.

 

To clear things up again the Granatelli fuel pump is for a TPI and the pump doesn't seem to be the problem since this is the second one I've had in there. As far as running the pump off the ALDL plud the wire isn't connected since i still have the same plug from the TBI. Everything was running fine a few months ago though. There may be a voltage problem but I haven't had a problem with it before and I also tested it a while ago. The new injectors are in and the car tried to start but it's still only running for a few seconds at best. I'm completely lost here.

 

Let me beat the horse once more. If you have 12+ volts to the pump and its a pump for a TPI system, and the fuel lines and sending unit are the same on TBI as TPI, and nothing is blocked or leaking and you don't get 38+ psi at the rail, YOU HAVE A BAD PUMP. If the injectors are letting gas go through them with only the key on, you have another problem.

 

Yeah, what he said(see above)

If you are not getting good pressure to the rails, either its leaking in the motor, or you are not getting the pressure to begin with.

 

I just got back from the garage and still no luck. I have the right voltage at the fuel pump and it's kicking on when it should. I tried to pinch off the return line and I still got low pressure. I pulled the spark plugs to see if any gas was leaking through the injectors and it's not. I just put in new accel injectors yesterday. The pump is pushing the fuel it just isn't putting out enough pressure. I really don't think it's a bad pump being as this is the second one I put in. The fuel filter is new and it's facing the right direction. The fuel lines are (as far as I know) the right ones which I bought off of a member of this site. The only thing I haven't changed is the fuel pump sending unit. The only difference I noticed though was the TBI sending unit has a breather line and the TPI doesn't. I tried to see if this was the problem by pinching off the breather line but still no luck. I think i've answered everything anyone can possibly ask now so please let me know if anything doesn't look right here. Thanks for all the help.

 

Then the problem is in the tank somewhere. Could be the hose between the pump and the assembly. Could be the pickup filter. Could be the pump. Could be poor pump grounding.

 

My 88 has a pulsator between the supply line, and the pump inside the tank, I believe it's the source of my slow leak down (rubber is probably getting hard like the valve rubber boot seals.) The pump came with a section of hose & clamps to replace it with, but i forgot to do it.

 

Thanks for the ideas. I'm looking for stock TPI fuel lines and a new sending unit so as soon as I find them I'll check that rubber line. I do remember now that I didn't change it, I just used the old one. If anyone is near Pittsburgh and has either the fuel lines or a sending unit please let me know. I need to get this done as soon as possible.