battleborn Posted March 25, 2013 Share Posted March 25, 2013 Have 88 MJ. Would seem that truck left factory with 4.0L engine and and had 2.5L fuel module in tank. Bosch pump just recently failed after few years and it never did fit right. The Walbro pump does not fit into module either. Has anyone had this experience with this. Concerned that the 2.5L pump will not flow enough to feed MPI. Napa specifications are 14lb.hr and 64psi. Link to comment Share on other sites More sharing options...
battleborn Posted March 26, 2013 Author Share Posted March 26, 2013 Picked up 2.5L fuel pump this afternoon. It definetly is a 2.5L module that has been installed into 4.0 MPI. Complete perfect fit. Still can't get my head around idea of 14lb.hr flow rate. That would be enough to prime rail and allow curb idle, just can't see enough volume when demand is there and engine is under load. If anybody has any information on this please I would greatly appreciate ant input befor this pump goes in tank and can't be returned. I am heavy equipment mechanic by trade, work on diesel engines ranging from 52 liters to 74 liters hope that I am not reading to much diesel basics into a gas engine. Link to comment Share on other sites More sharing options...
mjeff87 Posted March 27, 2013 Share Posted March 27, 2013 here is a pic of the two different pumps.....2.5 on bottom, 4.0 on top. I don't see how the 2.5 pump could supply enough PSI for the injectors to fire correctly in a 4.0. You should be able to swap a 4.0 pump into the pump assembly though, the top bracket is slotted so that it can be adjusted. Image Not Found Link to comment Share on other sites More sharing options...
battleborn Posted March 28, 2013 Author Share Posted March 28, 2013 I took some pictures of module, however I am not sure how to get them posted on here. This is definetly a 2.5L module though. I agree with you, I don't see how it would have enough flow to be able stay with demand while under load. At this point curiosity is driving me to install and see how the engine performs. If it doesn't work guess I have new transfer pump for future pump jobs. Planning on installing on Saturday and will post findings. If there is one out here there has to be more that have a 2.5L module. If anyone could line me out on how to post pictures here would awesome. Link to comment Share on other sites More sharing options...
mjeff87 Posted March 28, 2013 Share Posted March 28, 2013 I swapped a 4.0 into my 2.5 MJ (that's where that pic came from, it was during the swap). I was going to try to leave the 2.5 pump in it and see how it did, but I didn't want to chance it, so I swapped them. I think the 2.5 pump could supply the fuel volume needed, but not the pressure. Curious to see what you find out, please post up the results. Jeff edit: to post pics, you have to upload them to a hosting site (photobucket, flickr, etc) and then link them in your post. To link, paste the website address of the pic once hosted inside image brackets (). If using photobucket, click the "image links" link and then copy/paste the link into your post. Link to comment Share on other sites More sharing options...
battleborn Posted March 28, 2013 Author Share Posted March 28, 2013 I would be using the Bosch pump for sure if would fit into module. When I pulled the module out I noticed that the B+ terminal on pump was contacting upper bolt on support from twisting on module. I made sure when I put it together some years ago now that it was seucre to module, however still gave it the raised eyebrow when done. Even ordered and tried the Walbro pump and it didn't fit either. The only reason I am doing all of this now is to have the correct pump for module. I am really curious now about how this smaller fuel pump will perform. I searched high and low for even a used 4.0L module just to use different pump. I will definetly post results on this. I love this truck and they will bury me with it when I go, but there are somedays that it makes me pull my hair out. Thank You for the information on posting pics when I can get a chance to figure all of that out here I will post the pictures of the module and pump fit. I have been going through the grounds on this thing and WOW... They certainly didn't put much time or effert into that. Started with the ground due to issues with TPS, IAC, and rather developed engine miss, random no starts all at the same time. Found the post on here by criuser54 after I had pulled C101 connector and block ground and decided to start with ground something common to all systems before looking at ECM. Surfaces not cleaned as in paint and under grounded IMO. The C101 connection I am planning on repinning with Deutz HD connectors and just eliminate the 101. Between the low qualty pins and whatever that black sludge is supposed to be it is amazing that this has gone 25 years with out any issue. Link to comment Share on other sites More sharing options...
battleborn Posted June 24, 2013 Author Share Posted June 24, 2013 Update on this old topic. Just barely finished the engine work which ended up being quite extensive. The 2.5L fuel pump will work on 4.0L MPI engine and the pump fit into module as designed. Rail pressure is within spec. and I have not noticed any flow issues with pump at all. There is no hesitation under hard acceleration at high rpm issues at all. The fuel pump was not the only issue it had. Apparently resistor was aslo failing creating excessive current draw to fuel pump also. Link to comment Share on other sites More sharing options...
mjeff87 Posted June 25, 2013 Share Posted June 25, 2013 Very interesting. Thanks for the followup. Maybe I should try swapping my old 2.5 pump/assembly back into mine and see how it works. At least my fuel gauge would read correctly :) Jeff Link to comment Share on other sites More sharing options...
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